Low-density lipoprotein size,high-density lipoprotein concentration,and endothelial dysfunction in non-insulin-dependent diabetes

We examined endothelial function (nitric-oxide mediated) in 29 men with diet-treated non-insulin-dependent (Type 2) diabetes mellitus (NIDDM) and 18 male age-matched controls. Forearm blood flow was measured by venous occlusive plethysmography during intra-arterial administration of acetylcholine (ACh, 7.5 and 15 μg min⁻¹) and sodium nitroprusside (SNP, 3 and 10 μg min⁻¹). LDL particle size was estimated by non-denaturing gel electrophoresis. Serum lipids, blood pressure, and glycated haemoglobin were also measured. LDL particle size was smaller (p = 0.048) in the diabetic patients than controls. In the diabetic patients, LDL particle size was a significant positive predictor (p = 0.01) of the area under the dose–response curve for ACh, after adjusting for age, HbA_1c, systolic BP, and cholesterol (R² 0.20). In stepwise regression including serum lipid and lipoprotein concentrations and LDL particle size, decreased HDL cholesterol was the best predictor of an impaired vasodilatory response to ACh. Vasodilatory responses to sodium nitroprusside were not significantly correlated with LDL particle size or serum lipid and lipoprotein concentrations. We conclude that in men with NIDDM, small, dense LDL particle size is associated with abnormal endogenous release of nitric oxide. The contribution of small, dense LDL particles to the development of endothelial dysfunction and early diabetic vasculopathy may not, however, be as great as decreased HDL cholesterol. © 1997 John Wiley & Sons, Ltd.     

Effect of type 2 diabetes on various electrophoretic characteristics of low-density lipoprotein particles in women

Aims/hypothesis Coronary heart disease represents the leading cause of death in type 2 diabetic patients. As the small, dense LDL phenotype is a typical feature of the dyslipidaemic state found in type 2 diabetes, this characteristic could be an important mediator of the elevated coronary heart disease risk in this condition. We have therefore studied the effect of type 2 diabetes on various electrophoretic characteristics of LDL particles.Methods Potential differences in LDL peak particle size and in concentration of LDL cholesterol in small (<255 Å) and large (>260 Å) LDL particles were assessed by polyacrylamide gradient gel electrophoresis among 183 non-diabetic and 56 type 2 diabetic women.Results LDL peak particle size was significantly smaller in type 2 diabetic women than in non-diabetic women (p<0.0001). In addition, the proportion of small LDL particles (<255 Å) was higher in type 2 diabetic women, whereas the proportion of large LDL particles (>260 Å) was lower than in non-diabetic women (p<0.0002). Type 2 diabetic women also had the highest waist circumference and triglyceride levels (p<0.03). When subgroups of non-diabetic and type 2 diabetic women were individually matched (n=41) for similar waist circumference and triglyceride levels, the differences initially found in LDL peak particle size and in the proportion of small and large LDL particles remained significantly different between the two groups (p<0.01).Conclusions/interpretation These results provide evidence that type 2 diabetes may have an independent effect on LDL peak particle size and on the proportion of small and large LDL particles.     

Remarkably high prevalence of small dense low-density lipoprotein in Japanese men with coronary artery disease, irrespective of the presence of diabetes.

To examine how prevalence of the small dense LDL phenotype (LDL particle diameter < or =25.5 nm) is associated with coronary artery disease (CAD) in type 2 diabetic and non-diabetic Japanese men, an ethnic group with a low incidence of CAD, 85 non-diabetic men and 45 type 2 diabetic men with angiographically documented CAD, and 142 control men and 76 type 2 diabetic men without CAD were studied. Mean LDL particle diameter was determined using 2-16% polyacrylamide gel electrophoresis. LDL particle diameters in CAD patients were much smaller than those in controls (25.2+/-0.7 vs. 26.0+/-0.4 nm, mean+/-S.D., P<0.0001). LDL size was smaller in diabetic subjects (25.6+/-0.6 nm) and became even smaller in diabetics with CAD (25.0+/-1.0 nm). Prevalence of small dense LDL was markedly higher in both non-diabetic and diabetic CAD patients than that in non-diabetic and diabetic patients without CAD (71, 76, 23 and 42%, respectively). CAD patients had lower HDL-cholesterol and apo A1 levels, and higher triglyceride levels than those in diabetic and non-diabetic CAD-free patients, while total- and LDL-cholesterol levels were even lower in CAD group, and remnant-like particle-cholesterol, lipoprotein (a) and insulin levels were comparable among four groups. LDL size was significantly associated with triglyceride, HDL-cholesterol and glycemic control. Logistic regression analysis revealed that the small dense LDL phenotype was significantly associated with the incidence of CAD independent of low levels of HDL-cholesterol or high levels of triglyceride in both non-diabetic and diabetic cases. These results suggest that high prevalence of small dense LDL is a leading cause of CAD in both diabetic and non-diabetic Japanese men. Type 2 diabetes shows a greater capacity to reduce LDL size, which may contribute to the high incidence of CAD in the diabetic population.     

Alterations in apolipoprotein B-48 in the postprandial state in NIDDM

Summary The intestine is a major site of cholesterol synthesis and produces apolipoprotein B-48, which is critical for intestinal cholesterol absorption and secretion. The purpose of this study was to examine postprandial changes in apolipoprotein B-48 in diabetes. Six non-insulin-dependent diabetic patients and six non-diabetic control subjects were given a high-fat meal (1300 kcal) and blood samples were taken pre- and postprandially, from which the triglyceride-rich lipoprotein fraction was isolated by ultracentrifugation (density<1.006 g/ml). Apolipoprotein B-48 was separated on 4–15% gradient gels and quantified as a percentage of the fasting concentration by densitometric scanning. Total protein, triglyceride and cholesterol in the triglyceride-rich lipoprotein fraction, blood glucose, and serum insulin were also measured. Diabetic patients exhibited a postprandial triglyceride-rich apolipoprotein B-48 profile significantly different from that of control subjects (p<0.05). The triglyceride and total protein concentration in the triglyceride-rich lipoprotein fraction mirrored the post-prandial profile and apolipoprotein B-48 in both groups. Significantly different patterns for triglyceride (p<0.02) and total protein (p<0.05) following the fat-rich meal were observed in the two groups. Fasting and postprandial triglyceride-rich lipoprotein cholesterol and total apolipoprotein B were significantly higher in diabetic patients than in control subjects (p<0.05). Since apolipoprotein B-48 is the structural protein of intestinally-derived lipoprotein particles, these studies suggest an abnormality in intestinal lipoprotein metabolism in diabetes.Abbreviations TRL Triglyceride-rich lipoprotein - Apo-B48 apolipoprotein B-48 - apo-B100 apolipoprotein B-100 - apo E apolipoprotein E - VLDL very low density lipoprotein - NIDDM non-insulin-dependent diabetes     

High density-lipoprotein subfractions of patients using cardio-selective beta-blockers

Treatment of hypertension with beta-adrenergic blockers (BB) slightly increases plasma triglycerides and decreases high density lipoprotein (HDL) cholesterol levels. However, only little is known about BB-related lipid changes in patients with coronary artery disease (CAD), who usually a priori have decreased HDL cholesterol levels; and even less data exist on HDL subfraction cholesterol in these patients. We therefore quantified levels of lipids, lipoprotein lipids including HDL2 and HDL3 cholesterol, and apolipoproteins in 107 consecutive men undergoing elective coronary angiography. Of the 107 patients, 84 had angiographically established coronary atherosclerosis (1 lesion with 50% narrowing, CAD+), and 23 had no major lesion (CAD–); 67 were taking ß1-selective BB (metoprolol or atenolol) for treatment of angina and/or hypertension and 40 were not. Patients using BB had significantly higher cholesterol levels than patients not using BB (5.99 ± 0.93 vs. 5.63 ± 1.07 mmol/l, mean ± SD, p = 0.029). Their HDL cholesterol and HDL2 cholesterol levels were significantly lower (1.19 ± 0.27 vs. 1.28 ± 0.33 mmol/l, p = 0.048, and 0.22 ± 0.12 vs. 0.27 ± 0.18 mmol/l, p = 0.038, respectively). Accordingly, the total cholesterol/HDL cholesterol ratio was significantly higher in patients taking BB than in those not taking BB (5.23 ± 1.27 vs. 4.68 ± 1.63, p = 0.010). Considering CAD+ and CAD– patients separately, there was a trend towards lower HDL cholesterol and its subfractions with significantly lower HDL2 cholesterol in patients with BB in the CAD– group, suggesting a stronger dyslipidemic effect of BB in these patients with a priori normal or near normal baseline lipid levels.     

Plasma Lipoprotein Composition and Cholesteryl Ester Transfer from High Density Lipoproteins to Very Low Density and Low Density Lipoproteins in Patients with Non-insulin-dependent Diabetes Mellitus

We have examined cholesteryl ester transfer (CET) from HDL to low density and very low density lipoproteins (LDL and VLDL) and lecithin:cholesterol acyl transferase (LCAT) activity in plasma from 28 men with non-insulin-dependent diabetes mellitus (NIDDM) treated with diet alone or diet and sulphonylurea drugs and in 27 healthy non-diabetic controls. Patients and healthy subjects had similar LCAT activity, but CET was significantly higher in NIDDM 26.1 ± 11.5 μmol l⁻¹ h⁻¹) than in healthy men (17.8 ± 6.5 μmol l⁻¹ h⁻¹) (p = 0.001). Diabetic men also had higher CET compared to 15 healthy non-diabetic men (18.7 ± 5.6 μmol l⁻¹ h⁻¹) (p = 0.001) with similar serum lipids. CET activity was similar in patients treated with diet alone (24.8 ± μmol l⁻¹ h⁻¹) or with sulphonylureas (27.7 ± 15.8 μmol l⁻¹ h⁻¹). The Sf 0–12 fraction was significantly enriched with total cholesterol (p = 0.0001) and free cholesterol (p = 0.006) in diabetic subjects whether treated with diet alone or on sulphonylureas compared to the 15 non-diabetic controls matched for serum triglycerides. The free cholesterol/phospholipid, the free cholesterol/total protein and the free cholesterol/mass ratios were increased in the Sf 0–12 fraction in diabetic subjects (p < 0.01). These findings indicate that CET is accelerated in patients with NIDDM and that this may be due to the altered composition of acceptor lipoproteins.     

The effect of low density lipoprotein composition on the regulation of cellular cholesterol synthesis: a comparison in diabetic and non-diabetic subjects

This study investigates compositional differences in low density lipoprotein (LDL) subfractions and their relationship to cellular cholesterol synthesis. We examined ten normocholesterolaemic (serum cholesterol <6.5 mM) non-diabetic subjects (group 1) and compared them with ten normocholesterolaemic (group 2) and ten hypercholesterolaemic (group 3) (serum cholesterol >6.5 mM) type 2 (non-insulin-dependent) diabetic patients. Serum cholesterol levels for groups 1, 2 and 3 were 5.19±0.27, 5.20±0.27 and 7.51±0.31 mM. LDL₁ (density 1.006–1.028 g/l) and LDL₂ (1.028–1.063 g/l) were isolated by density gradient ultracentrifugation. A significantly greater proportion of cholesterol was carried in LDL₂ than LDL₁ in all groups. There was a significantly lower cholesterol/protein ratio in LDL₁ from the hypercholesterolaemic diabetic patients compared with controls. The LDL esterified/free cholesterol ratio was significantly greater in both LDL₁ and LDL₂ in the hypercholesterolaemic diabetic patients compared with the other two groups. There was a negative correlation between inhibition of cholesterol synthesis and the esterified/free cholesterol ratio of both LDL₁ (r=0.56,P<0.002) and LDL₂ (r=0.63,P<0.001). Cellular cholesterol of 41.0±0.3 g/mg cell protein in the hypercholesterolaemic diabetic patients was also significantly higher compared with values of 30.32±2.0 and 34.1±4.2 g/mg cell protein for the normocholesterolaemic non-diabetic and diabetic groups. In vitro LDL esterification led to a decrease in LDL receptor-mediated binding and resulted in a 40% reduction in the ability of the LDL to suppress cholesterol synthesis. The study demonstrates a relationship between the LDL esterified/free cholesterol ratio, LDL receptor binding and cellular cholesterol and may have implications for the understanding of hypercholesterolaemia in diabetes.     

Serum lipoprotein(a) concentrations and apolipoprotein(a) phenotypes in the families of NIDDM patients

Summary We studied the quantitative and qualitative characteristics of lipoprotein(a) [Lp(a)] as a function of apolipoprotein(a) [apo(a)] phenotype in 87 members (42 males, 45 females) of 20 diabetic families, 26 of whom were diagnosed with non-insulin-dependent diabetes mellitus (NIDDM) with moderate glycaemic control (HbA_1c7.1±1.2%). Apo(a) phenotyping was performed by a sensitive, high-resolution technique using SDS-agarose/gradient PAGE (3–6%). To date, 26 different apo(a) phenotypes, including a null type, have been identified. Serum Lp(a) levels of NIDDM patients and non-diabetic members of the same family who had the same apo(a) phenotypes were compared, while case control subjects were chosen from high-Lp(a) non-diabetic and low-Lp(a) non-diabetic groups with the same apo(a) phenotypes in the same family. Serum Lp(a) levels were significantly higher in NIDDM patients than in non-diabetic subjects (39.8±33.3 vs 22.3±19.5 mg/dl, p<0.05). The difference in the mean Lp(a) level between the diabetic and non-diabetic groups was significantly (p<0.05) greater than that between the high-Lp(a) non-diabetic and low-Lp(a) non-diabetic groups. An analysis of covariance and a least square means comparison indicated that the regression line between serum Lp(a) levels [log Lp(a)] and apo(a) phenotypes in the diabetic patient group was significantly (p<0.01) elevated for each apo(a) phenotype, compared to the regression line of the control group. These data, together with our previous findings that serum Lp(a) levels are genetically controlled by apo(a) phenotypes, suggest that Lp(a) levels in diabetic patients are not regulated by smaller apo(a) isoforms, and that serum Lp(a) levels are greater in diabetic patients than in non-diabetic family members, even when they share the same apo(a) phenotypes.Abbreviations Lp(a) Lipoprotein(a) - apo(a) apolipoprotein(a) - NIDDM non-insulin-dependent diabetes mellitus - TC total cholesterol - LDL low density lipoprotein - TG triglycerides - HDL-C high density lipoprotein-cholesterol - LDL-C low density lipoprotein-cholesterol - PBS phosphate buffered saline The first two authors contributed equally to this work     

Role of small dense low-density lipoprotein in coronary artery disease patients with normal plasma cholesterol levels

OBJECTIVES: The relationship between plasma low-density lipoprotein (LDL) cholesterol and the risk of coronary artery disease (CAD) is known, but the other characteristics of LDL, particularly particle size and density, are unclear. The relationship between small dense LDL phenotype and non-diabetic, normocholesterolemic CAD was investigated in 70 patients with angiographically documented CAD, and 38 age-matched control subjects. METHODS: Peak LDL particle diameter was determined by using 2-16% polyacrylamide gradient gel electrophoresis. Small dense LDL phenotype was defined as particle diameter equal to or less than 255 A. RESULTS: LDL particle diameters in patients with CAD were significantly smaller than those in controls (252.4 +/- 6.9 vs 259.3 +/- 8.8 A, mean +/- SD, p < 0.0001). Prevalence of small dense LDL was markedly higher in patients with CAD (72%) than in subjects without CAD (24%). CAD patients had significantly lower high-density lipoprotein (HDL)-cholesterol and apolipoprotein A-I levels (39.3 +/- 8.8 vs 49.8 +/- 12.0, 108.1 +/- 20.6 vs 122.9 +/- 20.1 mg/dl), and higher lipoprotein (a) and apolipoprotein B levels (28.8 +/- 30.4 vs 16.8 +/- 18.8, 96.5 +/- 21.8 vs 80.2 +/- 14.9 mg/dl) than non-CAD subjects, whereas total cholesterol, LDL-cholesterol, triglyceride, remnant-like particle cholesterol and insulin levels were not increased in CAD patients compared with non-CAD subjects. Stepwise regression analysis revealed that LDL particle size was the most powerful independent determinant of CAD (F value = 20.04, p < 0.0001). Logistic regression analysis revealed that small dense LDL phenotype [relative risk (RR) of 7.0, 95% confidence interval (95% CI) 2.4-20.1], low HDL-cholesterol (RR of 5.6, 95% CI 2.1-15.2), and increased apolipoprotein B (RR of 5.8, 95% CI 1.8-18.5) were independently associated with incidence of CAD. CONCLUSIONS: High prevalence of small dense LDL is a leading cause of CAD with even normal cholesterol levels.     

LDL subclasses in IDDM patients: relation to diabetic nephropathy

Summary To answer the question whether the elevation of LDL-cholesterol in IDDM patients with incipient and established diabetic nephropathy is accompanied by changes in LDL size or composition, we studied distribution of LDL particles in 57 normoalbuminuric [AER 7 (1–19) g/min, median and range], in 46 microalbuminuric [AER 50 (20–192) g/min] and in 33 proteinuric [AER 422 (233–1756) g/min] IDDM patients as well as in 49 non-diabetic control subjects with normoalbuminuria. The three diabetic groups were matched for duration of diabetes and glycaemic control. The mean particle diameter of the major LDL peak was determined by nondenaturing gradient gel electrophoresis. Composition and density distribution of LDL were determined in the subgroups of each patient group by density gradient ultracentrifugation. Normoalbuminuric IDDM patients had larger LDL particles than non-diabetic control subjects (260 Å vs 254 Å, p<0.05). LDL particle diameter was inversely correlated with serum triglycerides in all groups (p<0.05 for normoalbuminuric and p<0.001 for other groups). Triglyceride content of LDL was higher in three IDDM groups compared to control group (p<0.05). The elevation of LDL mass in microalbuminuric and proteinuric IDDM groups compared to normoalbuminuric IDDM group (p<0.05 for both) was mainly due to the increment of light LDL (density 1.0212–1.0343 g/ml). There were no significant changes in the density distribution or composition of LDL between the three diabetic groups. In conclusion the increase of LDL mass without major compositional changes suggests that the elevation of LDL in incipient and established diabetic nephropathy is primarily due to the increased number of LDL particles. The prevalence of atherogenic small dense LDL particles in IDDM patients with microalbuminuria and proteinuria is closely dependent on plasma triglyceride concentration.Abbreviations AER urinary album excretion rate - CETP cholesteryl ester transfer protein - IDDM insulin-dependent diabetes mellitus - CHD coronary heart disease - ApoB apolipoprotein B     

High density lipoprotein (HDL) particle composition in patients with end stage renal failure (ESRF) on chronic dialysis

Background: Hypertriglyceridaemia, low high density lipoprotein (HDL) cholesterol level and reduced LDL particle size are the major features of uraemic dyslipidaemia. They are also found in the Insulin Resistance Syndrome. Aim: To examine alterations in HDL composition in patients on chronic dialysis and their relationship with insulin resistance. Methods: HDL particle size was determined in 33 patients on chronic haemodialysis (HD), 27 on chronic ambulatory peritoneal dialysis (CAPD) and 32 control non-diabetic subjects (C) without renal disease by non-denaturing 3–30% polyacrylamide gradient gel electrophoresis. A weighted HDL particle size score was calculated taking into account both HDL particle size and percentage total HDL protein concentration of each HDL band of the individual. lipid and apolipoliprotein concentrations were determined in HDL2 and HDL3 particles obtained by sequential ultracentrifugation. In a subset of 24 control subjects and 22 subjects on HD, insulin sensitivity was also determined by an intravenous glucose tolerance test (IVGTT). Results: HDL particles were found to be more triglyceride enriched and apoAI depleted in subjects on HD even though plasma triglyceride level was highest in patients on CAPD. Five subpopulations of HDL particles were identified by gradient gel electrophoresis in all subjects combined. In the subgroup of subjects who underwent IVGTT, the weighted HDL particle size score correlated positively with HDL cholesterol level 0=0.6, p<0.0005), LDL particle size (r=0.47, p>0.001), and insulin sensitivity (r=0.48, p<0.001), and negatively with plasma triglyceride level (r=-0.37, p<0.01). Conclusions: We conclude that even though HDL cholesterol is reduced to a similar level in subjects on both forms of dialysis for end stage renal failure, abnormalities of HDL composition are more marked in subjects on HD. Reduction in HDL particle size is linked with insulin resistance and accompanies reduction in LDL particle size and hypertriglyceridaemia.     

Lipoprotein composition in NIDDM: effects of dietary oleic acid on the composition,oxidisability and function of low and high density lipoproteins

Summary Oxidation of low density lipoprotein (LDL) plays an important role in the pathogenesis of atherosclerosis and is related to the fatty acid composition which is altered in diabetes mellitus. This study examines the relationship between the fatty acid composition of LDL and high density lipoprotein (HDL) and lipoprotein oxidation. A group of nine non-insulin-dependent diabetic (NIDDM) patients were compared to seven healthy control subjects before and after a high monounsaturated diet. Lipoproteins were isolated and oxidisability was measured by conjugated diene formation and lipid peroxide analysis. Serum HDL cholesterol was significantly lower in the diabetic patients. LDL cholesteryl ester linoleic acid in the diabetic patients was significantly higher at baseline and decreased after diet (p<0.05) while oleic acid increased in both diabetic and non-diabetic subjects (p<0.05). HDL cholesteryl ester oleic acid was lower in the diabetic patients compared with control subjects (p<0.05) before diet and it increased significantly after diet (p<0.05). LDL lipid peroxides and conjugated diene formation were related to LDL glycation (r=0.46, p<0.05 and r=0.49, p<0.05, respectively). Both decreased following diet (lipid peroxides for diabetic patients from 476±30 to 390±20 nmol/mg protein p<0.05 and for control subjects from 350±36 to 198±30 nmol/mg protein p<0.05). HDL conjugated diene formation decreased in both groups after diet but only significantly in the control group (55.4±7.5 to 53.2±6.7 nmol/mg protein for diabetic patients and 45.8±6.4 to 31.6±4.8 nmol/mg protein p<0.05 for control subjects). There was a positive correlation between LDL lipid peroxide formation and percentage of cholesteryl ester linoleic acid in LDL from diabetic patients (r=0.61, p<0.05) and control subjects (r=0.91, p<0.01). Fatty acid composition of LDL was reflected in the composition of HDL. In the presence of HDL lipoprotein peroxidation decreased. This decrease in lipoprotein peroxidation was positively related to the percentage of linoleic acid in LDL (r=0.71, p<0.05). This study confirms the close relationship between the fatty acid composition of LDL and HDL and demonstrates the importance of the fatty acid composition of the cholesteryl ester fraction in relation to LDL oxidation in diabetes. Linoleic acid in HDL appears to be a protecting factor against oxidation.Abbreviations BHT Butylated hydroxytoluene - EDTA ethyl-enediaminetetraacetic acid - TBARS thiobarbituric reacting substances - HPLC high performance liquid chromatography - MDA malondialdehyde - HbA_1c glycated haemoglobin     

Increased circulating malondialdehyde-modified LDL levels in patients with coronary artery diseases and their association with peak sizes of LDL particles

Recent establishment of a sensitive ELISA system using antibodies against malondialdehyde-modified low density lipoprotein (MDA-LDL) made it possible to determine the circulating oxidized lipoprotein levels. Here, we investigated the serum levels of MDA-LDL in 62 patients with coronary artery disease (CAD) compared with the levels in 42 patients without CAD [groups CAD(+) and CAD(-), respectively], which are adjusted for age, serum total cholesterol, LDL and high density lipoprotein cholesterol, and triglyceride levels. Serum MDA-LDL levels were 113.4+/-49.1 IU/L in CAD(+), which were significantly higher than the levels in CAD(-) (85.2+/-22.5 IU/L, P<0.0005). The ratio of MDA-LDL/LDL cholesterol was 0.95+/-0.32 in CAD(+), indicating a significant increase compared with the ratio in CAD(-) (0.68+/-0.19, P<0.0005). The positive correlation of MDA-LDL level and the ratio of MDA-LDL/LDL cholesterol with intima-media thickness in carotid arteries was observed. Age was not clearly associated with the MDA-LDL level (P=0.865). The serum MDA level was positively correlated with LDL cholesterol (P<0.0001) and with triglycerides (P<0.001) and negatively correlated with high density lipoprotein cholesterol (P<0.05). Furthermore, the MDA-LDL level was negatively correlated with the peak size of the LDL particle (P<0.01). The LDL subclasses that were identified by using the sera collected from the subjects by sequential ultracentrifugation showed that the ratios of MDA-LDL/apolipoprotein B in LDL3 and LDL4 were nearly 3-fold higher than those in LDL1 and LDL2 for CAD(+) and CAD(-). These results indicate that the circulating MDA-LDL level is increased in CAD(+), independent of the serum LDL cholesterol level but in association with the peak size of LDL particles. The measurement of serum MDA-LDL level may be useful for the identification of patients with advanced atherosclerosis.     

Asymptomatic hyperglycaemia is associated with increased intimal plus medial thickness of the carotid artery

Summary Atherosclerotic changes have not been demonstrated directly in asymptomatic hyperglycaemic non-diabetic subjects, although high mortality due to coronary heart disease has been reported. We measured arterial wall thickness non-invasively, in order to directly demonstrate atherosclerosis of the carotid arteries of hyperglycaemic non-diabetic subjects and to evaluate its risk factors.The thicknesses of the intimal plus medial complex (IMT) of the carotid arteries of 112 asymptomatic hyperglycaemic non-diabetic subjects (aged 22–81, 95 males and 17 females) were compared with those of 55 healthy male subjects and 211 non-insulin-dependent NIDDM male diabetic patients. The subjects were subgrouped into impaired glucose-tolerant (IGT) subjects who had a 2-h glycaemic level of more than 7.8 mmol/l, and non-IGT subjects whose 2-h glycaemic levels were within 6.7–7.7 mmol/l.Non-IGT and IGT subjects showed significantly greater IMTs than age-matched healthy males and showed no significant differences compared to age-matched NIDDM patients. Multivariate analysis demonstrated that the risk factors for IMT of non-IGT and IGT subjects were age and systolic blood pressure. According to data on the accumulation of atherogenic risks (hypertension, dyslipidaemia, and smoking), IMT increased linearly in non-IGT and IGT subjects. However, non-IGT and IGT subjects without hyperlipidaemia, hypertension, or smoking risk still had significantly greater IMT than age-matched normal males (1.019±0.063 vs 0.770±0.111 mm, p<0.05). Prevalence of ECG-indicated coronary heart disease was significantly higher in hyperglycaemic non-diabetic subjects and NIDDM with increased carotid arterial wall thickness (IMT 1.1 mm) than in those without increased thickness (IMT<1.1 mm). Asymptomatic hyperglycaemic non-diabetic subjects have increased thickness of their carotid arteries compared to age-matched male NIDDM patients. As one of several independent risk factors, mild hyperglycaemia advances atherosclerosis, which leads to coronary heart disease.Abbreviations IMT Intimal plus medial complex - NIDDM non-insulin-dependent diabetes mellitus - IGT impaired glucose tolerance - CHD coronary heart disease - T-Chol serum total cholesterol - HDL-C high-density lipoprotein cholesterol - TG serum triglycerides     

Lipid and lipoprotein abnormalities in diabetic patients with peripheral vascular disease

Coronary heart disease in insulin-dependent (IDDM) and in non-insulin-dependent diabetes (NIDDM) is associated with lipid and lipoprotein changes favouring atherosclerosis. Whether lipid and lipoprotein abnormalities are associated also with peripheral vascular disease in both types of diabetes is largely unknown. Therefore, we studied lipid and lipoprotein levels and their association with claudication in a representative sample of diabetic and non-diabetic subjects in East Finland. Altogether 87 subjects had IDDM (43 men, 44 women), 264 subjects NIDDM (126 men, 138 women) and 120 subjects were non-diabetic controls (63 men, 57 women). Patients with IDDM had an increased level of HDL and HDL2-cholesterol and patients with NIDDM a decreased level of HDL and HDL2-cholesterol and an increased level of total, LDL and VLDL triglycerides than did non-diabetic subjects. Analyses in both types of diabetes by claudication status revealed that total and LDL-cholesterol and total and VLDL triglycerides tended to be higher and HDL and HDL2-cholesterol lower in those having claudication as compared to those without a claudication symptom. Similarly, total cholesterol/HDL-cholesterol ratio and LDL-cholesterol/HDL-cholesterol ratio were also more atherogenic in patients with claudication than in those without claudication. In conclusion, our results indicate that in both types of diabetes peripheral vascular disease is associated with lipid and lipoprotein abnormalities favouring atherosclerosis.     

Serum cholesterol and cholesterol and lipoprotein metabolism in hypercholesterolaemic NIDDM patients before and during sitostanol ester-margarine treatment

Summary Cholesterol absorption and metabolism and LDL and HDL kinetics were investigated in 11 hypercholesterolaemic non-insulin-dependent diabetic men off and on a hypolipidaemic treatment with sitostanol ester, (3 g sitostanol daily) dissolved in rapeseed oil margarine, by a double-blind crossover study design. Serum total, VLDL and LDL cholesterol and apoprotein B fell significantly by 6±2, 12±6, 9±3 and 6±2%, mean ±SEM, and HDL cholesterol was increased by 11±4% (p<0.05) by sitostanol ester. LDL cholesterol and apoprotein B were significantly decreased in the dense (1.037–1.055 g/ml), but not light, LDL subfraction due to a significantly diminished transport rate for LDL apoprotein B, while the fractional catabolic rate was unchanged. HDL kinetics, measured with autologous apoprotein AI, was unaffected by sitostanol ester. Cholesterol absorption efficiency was markedly reduced from 25±2 to 9±2% (p<0.001) during sitostanol ester followed by proportionately decreased serum plant sterol proportions. Cholesterol precursor sterol proportions in serum, fecal neutral sterol excretion, and cholesterol synthesis, cholesterol transport, and biliary secretion were all significantly increased by sitostanol ester. We conclude that the sitostanol ester-induced decrease in cholesterol absorption compensatorily stimulated cholesterol synthesis, had no effect on fractional catabolic rate, but decreased transport rate for LDL apoprotein B so that serum total, VLDL and LDL cholesterol levels were decreased. Dietary rapeseed oil margarine rich in sitostanol ester was well tolerated, appears to be safe from the nutritional point of view and effective for lowering VLDL and LDL cholesterol and increasing HDL cholesterol in hypercholesterolaemic non-insulin-dependent diabetic subjects.Abbreviations Apo apoprotein - NIDDM non-insulin-dependent diabetes mellitus - VLDL very low density lipoprotein - IDL intermediate density lipoprotein - LDL low density lipoprotein - HDL high density lipoprotein - FCR fractional catabolic rate - TR transport rate Presented in part at the 65th Scientific Sessions of the American Heart Association, New Orleans, November 1992 (Circulation 1992; 86[Suppl I]: I-404)     

A preponderance of small dense LDL is associated with specific insulin,proinsulin and the components of the insulin resistance syndrome in non-diabetic subjects

Summary Recently, the presence of small dense low density lipoprotein (LDL) has been postulated to be a stronger risk factor for coronary heart disease than large LDL. While small dense LDL has been associated with individual components of the insulin resistance syndrome such as hypertension, high triglyceride level, low high density (HDL) cholesterol, and diabetess mellitus, there has been little work exploring whether LDL size is decreased in subjects with multiple metabolic disorders. We examined the association of LDL size and pattern to specific insulin (which does not cross-react with proinsulin), proinsulin, increased triglyceride, decreased HDL, hypertension and impaired glucose tolerance in 488 non-diabetic subjects from the San Antonio Heart Study. LDL size was significantly related to specific insulin, proinsulin and the fasting proinsulin/insulin ratio. Small dense LDL was significantly associated with high triglyceride level, decreased HDL cholesterol, hypertension and impaired glucose tolerance. LDL size (å) decreased in a stepwise fashion with increasing number of the metabolic disorders described above (zero 262.6±9.4; one 257.0±9.3; two 256.4±9.4; three 249.0±9.1; and four 244.9±9.0). These results were similar in men and women and in non-Hispanic whites and Mexican Americans. The association between LDL size and the number of metabolic disorders remained statistically significant even after adjustment for obesity, body fat distribution, gender, ethnicity, proinsulin and insulin concentrations. Furthermore, decreases in LDL size are also significantly associated with both a selective beta-cell defect (as estimated by the fasting proinsulin/insulin ratio) and insulin resistance (as estimated by the fasting insulin concentrations) although the association was some-what stronger for the latter. We conclude that small dense LDL may form part of the insulin resistance syndrome in non-diabetic subjects.Abbreviations BMI Body mass index - LDL low density lipoprotein - HDL high density lipoprotein - IGT impaired glucose tolerance - NIDDM non-insulin-dependent diabetes mellitus - WHR waist-hip ratio     

Increased hepatic secretion of very-low-density lipoprotein apolipoprotein B-100 in NIDDM

Summary We measured the hepatic secretion of very-low-density lipoprotein apolipoprotein B-100 (VLDL apoB) using a stable isotope gas-chromatography mass-spectrometry method in six patients with non-insulin-dependent diabetes mellitus (NIDDM) (four males, two females, age 57.5±2.2 years (mean±SEM), weight 88.2±5.5 kg, glycated haemoglobin (HbA₁) 8.5±0.5%, plasma total cholesterol concentration 5.7±0.5 mmol/l, triglyceride 3.8±0.9 mmol/l, high-density lipoprotein (HDL) cholesterol 1.0±0.1 mmol/l) and six non-diabetic subjects matched for age, sex and weight (four males, two females, age 55.7±2.8 years, weight 85.8±5.6 kg, HbA₁ 6.5±0.1%, plasma total cholesterol concentration 5.7±0.5 mmol/l, triglyceride 1.2±0.1 mmol/l, HDL cholesterol 1.4±0.1 mmol/l). HbA₁, plasma triglyceride and mevalpnic acid (an index of cholesterol synthesis in vivo) concentrations were significantly higher in the diabetic patients than in the non-diabetic subjects (p=0.006, p=0.02 and p=0.004, respectively). VLDL apoB absolute secretion rate was significantly higher in the diabetic patients compared with the non-diabetic subjects (2297±491 vs 921±115 mg/day, p<0.05), but there was no significant difference in the fractional catabolic rate of VLDL apoB. There was a positive correlation between VLDL apoB secretion rate and (i) fasting C-peptide (r=0.84, p=0.04) and (ii) mevalonic acid concentration (r=0.83, p<0.05) in the diabetic patients but not in the non-diabetic subjects. There was also a significant positive association between plasma mevalonic acid and plasma C-peptide (r=0.82, p<0.05) concentrations in the diabetic patients. We conclude that in NIDDM, there is increased hepatic secretion of VLDL apoB which may partly explain the dyslipoproteinaemia seen in this condition. We suggest that increased secretion of this apolipoprotein may be a consequence of resistance to the inhibitory effect of insulin on VLDL apoB secretion. Insulin resistance may also be the mechanism by which cholesterol synthesis, a regulator of apoB secretion, is increased in NIDDM.Abbreviations ApoB Apolipoprotein B-100 - VLDL very-low-density lipoprotein - GCMS gas-chromatography mass-spectrometry - MVA mevalonic acid - Hep G2 hepatoma G2 - -KIC -ketoisocaproic acid - TC total cholesterol - TG triglyceride - NEFA non-esterified fatty acids - FSR fractional secretion rate - ASR absolute secretion rate - m/z mass to charge ratio - CV coefficient of variation     

The Regulation of Post-prandial Cellular Cholesterol Metabolism in Type 2 Diabetic and Non-diabetic Subjects

The purpose of the study was to determine the effect of diabetes on the regulation of postprandial cholesterol metabolism. Four groups of patients (n = 8 for each group) were examined: Type 2 diabetic patients with and without hypercholesterolemia and nondiabetic subjects with and without hypercholesterolaemia. Serum lipoproteins, lipoprotein composition, cellular cholesterol, and cellular cholesterol synthesis were measured before and 4 h after a high calorie meal. The BMI for the hypercholesterolaemic diabetic patients of 31.5 ± 0.95 (SEM) was significantly higher than that for the control group of 26.2 ± 1.0 (p < 0.01). Fasting triglyceride levels were significantly higher in the normocholesterolaemic and hypercholesterolaemic diabetic patients and in the hypercholesterolaemic non-diabetic subjects (1.45 ± 0.22, 2.27 ± 0.34, and 1.58 ± 0.18 mmol l^?1, respectively) compared with normocholesterolaemic non-diabetic subjects (0.75 ± 0.12 mmol l^?1: p < 0.01). The normocholesterolaemic and hypercholesterolaemic diabetic subjects had significantly lower fasting serum high density lipoprotein (HDL) (1.06 ± 0.08 and 1.04 ± 0.06 mmol l^?1) compared to the corresponding non-diabetic groups (1.29 ± 0.11 and 1.45 ± 0.17 mmol l^?1, p < 0.05). The esterified/free cholesterol ratio of very low density lipoprotein (including chylomicrons VLDL-C) decreased postprandially in all groups with an overall decrease of 1.33 to 0.83 (p < 0.01). Fasting cellular cholesterol in mononuclear leucocytes from normocholesterolaemic diabetic patients was similar to that for hypercholesterolaemic diabetic (36.8 ± 1.2 vs 40.6 ± 5.5 mg g^?1 protein) and non-diabetic subjects (36.7 ± 6.8 mg g^?1 protein) and significantly greater than cholesterol in cells from control subjects (29.7 ± 1.5 mg g^?1 protein, p < 0.05). In cells from control subjects only, there was a significant postprandial increase in cholesterol to 39.4 ± 5.2 mg g^?1 protein (p < 0.05) and a corresponding postprandial reduction in cholesterol synthesis from 149 ± 34 to 102 ± 33 nmol g^?1 cell protein (p < 0.05). These results demonstrate a lack of correlation between serum and cellular cholesterol in diabetic patients and an inability to suppress cellular cholesterol synthesis postprandially in these patients. The differences may, in part, explain the increased deposition of cholesterol in atheromatous plaques in normocholesterolaemic diabetic patients.     

Relationship between postheparin plasma lipases and high-density lipoprotein cholesterol in different types of diabetes

Summary We measured serum lipids, lipoproteins and postheparin plasma lipases, lipoprotein lipase and hepatic lipase, in 12 female patients with Type 1 (insulin-dependent) diabetes (postglucagon C-peptide undetectable), in 11 female insulin-treated patients with Type 2 (non-insulin-dependent) diabetes (postglucagon C-peptide >0.60 nmol/l) and in 16 non-diabetic female control subjects. These three groups of subjects were similar with respect to age and obesity. Insulin dose was similar in patients with Type 1 and with Type 2 diabetes. HDL and HDL₂ cholesterol were lower in patients with Type 2 diabetes than in non-diabetic control subjects (p<0.05) but did not differ between patients with Type 1 diabetes and non-diabetic control subjects. No difference in lipoprotein lipase activity was seen between the groups. The highest levels of lipoprotein lipase and hepatic lipase activities were observed in patients with Type 2 diabetes. Lipoprotein lipase activity correlated significantly with HDL cholesterol in patients with Type 1 diabetes (p<0.01) and in patients with Type 2 diabetes (p<0.001) but not in control subjects. Hepatic lipase activity did not correlate significantly with HDL cholesterol in any of the groups. In conclusion, postheparin plasma lipoprotein lipase and hepatic lipase activities do not seem to explain the difference in HDL cholesterol concentration between patients with Type 1 and Type 2 diabetes.