Gemfibrozil therapy in primary type II hyperlipoproteinemia: effects on lipids, lipoproteins and apolipoproteins

Gemfibrozil lowers triglycerides, low density lipoprotein (LDL) and very low density lipoprotein (VLDL) cholesterol. It also promotes a significant increase of high density lipoprotein (HDL) cholesterol. It has been established that normalization of apolipoproteins is an important protective factor against atherosclerosis. The present report examines the effectiveness of 12 months of gemfibrozil treatment on plasma lipids and apolipoproteins in types IIa (VLDL 18 +/- 2 mg cholesterol/dL) and IIb (VLDL 58 +/- 7 mg cholesterol/dL) hypercholesterolemic patients. Gemfibrozil lowered plasma triglycerides, VLDL cholesterol and apolipoprotein B (apoB), increased HDL cholesterol and apoAI levels in both groups, and induced a very substantial reduction in LDL cholesterol in type IIa patients only. Even though HDL particles were enriched in cholesterol, indicating improvement in the reverse cholesterol transport and lower risk of atherosclerosis in both groups, it is important to note that production of cholesterol-poor LDL particles and reduction in LDL cholesterol and the LDL/HDL cholesterol ratio were observed only in the normotriglyceride group (type IIa). Due to the initially elevated concentration of plasma triglycerides and VLDL in type IIb patients and the increased catabolism of VLDL to LDL during gemfibrozil therapy, this drug has a more efficient regulating effect on LDL particles in type IIa compared with type IIb hyperlipidemia.     

Clinical significance of HbA<Subscript>1c</Subscript> as a marker of circulating lipids in male and female type 2 diabetic patients

Diabetic patients with accompanied (but often unnoticed) dyslipidemia are soft targets of cardiovascular deaths. An early intervention to normalize circulating lipids has been shown to reduce cardiovascular complications and mortality. Glycated hemoglobin (HbA_1c) is a routinely used marker for long-term glycemic control. This investigation is an attempt to evaluate the diagnostic value of HbA_1c in predicting diabetic dyslipidemia. Venous blood samples were collected from 2,220 type 2 diabetic patients (ages, 35–91 years; male/female ratio, 1.07). The sera were analyzed for HbA_1c, fasting blood glucose (FBG), total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL) and low-density lipoprotein cholesterol (LDL). The levels of HbA_1c did not differ significantly between males (8.33 ± 0.06%) and females (8.47 ± 0.07%), whereas female patients had significantly higher FBG (10.01 ± 0.13 mmol/l) than males (9.31 ± 0.11 mmol/l). HbA_1c showed direct and significant correlations with cholesterol, triglycerides and LDL and inverse correlation with HDL. Female diabetic patients had significantly higher levels of serum cholesterol (5.42 ± 0.03 vs. 5.18 ± 0.03 mmol/l) and HDL (1.32 ± 0.01 vs. 1.12 ± 0.01 mmol/l) as compared to males. There was no significant difference in triglycerides and LDL between the two genders. Older patients (>70 years) had significantly lower FBG, cholesterol, triglycerides and LDL. There was a linear and significant increase in triglycerides in the patients of both genders with impaired glycemic control. Both male and female patients with worse glycemic control (HbA_1c > 9%) had significantly high cholesterol and LDL levels. Serum HDL showed a significant and inverse relationship with uncontrolled hyperglycemia in females but not in males. These findings clearly suggest that HbA_1c can provide valuable supplementary information about the extent of circulating lipids besides its primary role in monitoring long-term glycemic control. Further studies are warranted to reinforce the potential of HbA_1c as a biomarker for screening of high-risk diabetic patients.     

Low density lipoprotein cholesterol: An association with the severity of diabetic retinopathy

Summary Diurnal profiles of total and lipoprotein cholesterol and triglycerides were measured in 11 insulin-dependent diabetic subjects without retinopathy, 10 with background and 10 with proliferative retinopathy. The groups were closely matched for age and duration of diabetes. Total cholesterol levels were higher in patients with proliferative (5.6±0.5 mmol/l) than background (5.1±0.7 mmol/l) or no retinopathy (4.6±0.8 mmol/l, trend test; p < 0.003), due to raised levels of low density lipoprotein (LDL) cholesterol (3.8±0.9, 3.2±0.6 and 2.8±0.8 mmol/l respectively; p < 0.02). High density lipoprotein (HDL) levels were similar in patients with and without retinopathy and HDL/ LDL ratios were lower with more severe retinopathy (p < 0.025). Cholesterol levels were similar in diabetic subjects without retinopathy and in 12 normal subjects. Triglyceride levels were not related to retinopathy and no measure of plasma lipids correlated with HbA₁ or 24-h mean plasma glucose. Total and LDL cholesterol were weakly inversely correlated with creatinine clearance but the association with retinopathy was independent of this effect.     

Adverse effects of obesity on lipid and lipoprotein levels in insulin-dependent and non-insulin-dependent diabetes

We studied the association of obesity with lipid and lipoprotein concentrations in 92 patients (49 men, 43 women) with insulin-dependent diabetes (IDDM), in 305 patients (152 men, 153 women) with non-insulin-dependent diabetes (NIDDM), and in 122 nondiabetic control subjects (65 men, 57 women). Obesity (body mass index, BMI) was associated with abnormal lipid and lipoprotein levels only in the presence of diabetes, and lipid and lipoprotein changes were substantially more abnormal in patients with NIDDM than in patients with IDDM. In men and women with NIDDM, obesity was associated with low high-density lipoprotein (HDL) and HDL2 cholesterol and high total, low-density lipoprotein (LDL), and very low-density lipoprotein (VLDL) triglyceride concentrations. In men with IDDM, obesity was related only to low HDL and HDL2 cholesterol and in women with IDDM to low HDL3 cholesterol. BMI and diabetes status had a statistically significant interaction (analysis of variance) with respect to HDL and HDL2 cholesterol and total and VLDL triglycerides, indicating that the effects of obesity on lipids and lipoproteins were more severe in patients with diabetes than in nondiabetic subjects. In conclusion, obesity and diabetes status have an unfavorable interaction that results in multiple pathologic lipid and lipoprotein changes, particularly in NIDDM.     

Regulation of low-density lipoprotein particle size distribution in NIDDM and coronary disease: importance of serum triglycerides

Summary An increase of low-density lipoprotein triglycerides (LDL-Tg) was found to be an independent coronary artery disease (CAD) risk factor for non-insulin-dependent diabetic (NIDDM) patients in a recent prospective study. We examined the composition and size of LDL particles in 50 NIDDM men with angiographically verified CAD (NIDDM+ CAD+) and in 50 NIDDM men without CAD (NIDDM+ CAD–) as compared to 50 non-diabetic men with CAD (NIDDM– CAD+) and 31 non-diabetic men without CAD (NIDDM– CAD–). The groups had similar ranges of age and BMI LDL particle size was determined by gradient gel electrophoresis, and LDL was isolated by sequential ultracentrifugation for compositional analyses. Serum Tg was increased in NIDDM patients as compared to non-diabetic subjects (p<0.05), and in patients with CAD as compared to subjects without the disease (p<0.05). LDL cholesterol was lower in NIDDM patients than in non-diabetic subjects (p<0.001). Mean diameter of LDL particles was less than 255 å, but closely comparable in all groups. The presence of NIDDM was associated with increases of Tg and protein but lowering of free cholesterol in LDL (p<0.005 for all). In multivariate regression analyses neither NIDDM nor CAD were associated with LDL particle size, but serum Tg was the major determinant of LDL size in both NIDDM and non-diabetic subjects (p<0.001). When the patients were divided into quartiles according to fasting serum Tg levels, the LDL particle size and free cholesterol content decreased, but Tg and protein contents of LDL particles increased from the lowest to the highest Tg quartile (analysis of variance p<0.001 for all). When the subjects were categorized into two groups according to the median of VLDL-Tg (1.10 mmol/l) LDL size was associated with VLDL-Tg in the high but not in the low VLDL-Tg group. We conclude that in NIDDM patients with or without CAD serum Tg is the major determinant of the properties of LDL particles. The clinical implication is that in NIDDM serum Tg should be as low as possible to prevent atherogenic changes in LDL.Abbreviations NIDDM Non-insulin-dependent diabetes mellitus - CAD coronary artery disease - HDL high-density lipoprotein - LDL low-density lipoprotein - VLDL very-low-density lipoprotein - apoB apolipoprotein B - HL hepatic lipase - LPL lipoprotein lipase - CETP cholesteryl ester transfer protein - PL phospholipids - ANOVA analysis of variance - Tg triglycerides - FC free cholesterol     

Analysis of plasma lipids and apolipoproteins in insulin-dependent and noninsulin-dependent diabetics

Plasma triglycerides, cholesterol, high-density lipoprotein (HDL) cholesterol, and apolipoproteins (apo) A-I, A-II, C-II, and C-III were determined and analyzed in 170 diabetic patients and 46 age-matched healthy normal subjects. The diabetics were separated into two groups: insulin-dependent diabetes mellitus (IDDM, n = 78) and noninsulin-dependent diabetes mellitus (NIDDM, n = 92). Significantly increased triglycerides, low HDL cholesterol, and normal cholesterol levels were found in the diabetics. The lipid profiles were similar in the IDDM and NIDDM groups. Plasma apo A-I, but not apo A-II, was low in both groups of diabetics. However, only in the IDDM subjects was there a statistically significant decrease in apo A-I when compared to normal subjects. The decreased apo A-I level negatively correlated with plasma triglycerides. Apo C-II and apo C-III were slightly increased in the diabetics compared to normal subjects. Apo C-II and apo C-III levels significantly correlated with plasma triglycerides (apo C-II, r = 0.70, P less than 0.0001; apo C-III, r = 0.71, P less than 0.0001). Only apo C-II correlated with total cholesterol. Thirty-eight to forty-two percent of the IDDM and NIDDM subjects had a clinical diagnosis of coronary artery disease (CAD) and/or peripheral arteriovascular disease (PAD). In the IDDM subjects, but not in the NIDDM subjects the incidence of CAD and/or PAD was associated with the decreased apo A-I levels as evaluated by a univariate analysis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of Bezafibrate and Simvastatin in the Treatment of Dyslipidaemia in Patients with NIDDM

Fibrates and HMG CoA reductase inhibitors are commonly used in the treatment of diabetic dyslipidaemia. However, these two groups of drugs have not been compared in diabetic patients in a randomized controlled trial. Therefore, a multicentre study was performed in 73 subjects with non-insulin-dependent (Type 2) diabetes mellitus (NIDDM) and combined hyperlipidaemia (serum cholesterol 6.2–10.0 mmol l⁻¹, serum triglycerides 2.3–10.0 mmol l⁻¹), comparing the efficacy of 400 mg bezafibrate with 10 mg simvastatin in a double-blind fashion. Treatment with bezafibrate during 12 weeks reduced serum triglycerides significantly more than simvastatin (−41 % vs −22 %, p < 0.001) and increased HDL cholesterol more (bezafibrate: + 17 % vs simvastatin: + 9 %, p < 0.05). LDL cholesterol levels decreased by 14 % (p < 0.001) during simvastatin and increased by 21 % (p < 0.01) during bezafibrate. This increase in LDL cholesterol was positively correlated with fasting serum triglycerides (p < 0.001) and was associated with a reduction of the serum apolipoprotein B concentration, suggesting an increase in LDL particle size. Metabolic control of diabetes (fasting glycaemia; HbA_1c) and insulin secretion (C-peptide levels) were unaffected by both treatments. The incidence of side-effects during treatment was similar for both drugs. Thus, 400 mg bezafibrate mainly increases HDL cholesterol and lowers serum triglycerides but at the expense of an increase in LDL cholesterol; 10 mg simvastatin lowers LDL cholesterin more effectively but has a smaller effect on HDL cholesterol and triglycerides. © 1997 John Wiley & Sons, Ltd.     

Lipoprotein compositional abnormalities in type 1 (insulin-dependent) diabetic patients

Patients with type 1 (insulin-dependent) diabetes mellitus in good metabolic control usually have normal plasma lipid levels yet they have an increased incidence of vascular complications. Abnormalities in the distribution and composition of lipoprotein subfractions might in part be responsible for the macroangiopathy seen in type 1 diabetes mellitus. The plasma lipids, lipoproteins and apolipoproteins were studied in 9 type 1 diabetic patients during conventional insulin therapy and in 14 healthy controls. Plasma lipoproteins were analysed by ultracentrifugation in a zonal rotor to evaluate their concentrations and flotation properties and for compositional analysis. In diabetic patients the mean glycosylated haemoglobin (HbA_1c) was 9.44±1.02% and the plasma lipid concentrations were not significantly different from healthy controls. The very low density lipoprotein (VLDL) subclass cholesterol concentrations were no different in diabetic patients and control subjects, but the VLDL cholesterol/triglyceride ratio was significantly lower in diabetic patients than in control subjects (0.34±0.05 vs 0.85±0.14; p<0.05). The flotation rate of LDL₂, the major component of low density lipoprotein (LDL) was lower in the diabetic patients compared with the control subjects. The cholesterol concentrations of intermediate density lipoprotein and LDL₃, the minor component of LDL, were significantly higher (0.17±0.03 and 0.83±0.14 mmol/l respectively) in diabetic patients than in control subjects (0.05±0.02 and 0.24±0.08 mmol/l). The flotation properties and cholesterol concentrations of the high density lipoprotein (HDL) subclass, and the protein-lipid composition of LDL₂, HDL₂ and HDL₃, were no different in diabetic patients and control subjects. Diabetic patients had lower apoprotein AII and higher CII and E levels than control subjects. the plasma lipoproteins in type 1 diabetes mellitus are characterized by increased intermediate density lipoprotein and LDL₃ concentrations and by abnormal LDL₂ flotation properties. These lipoprotein abnormalities might have a role in atherogenesis in type 1 diabetic patients since similar alterations were associated in some recent epidemiological studies with an increased incidence of cardiovascular disease in non-diabetic patients.     

Normal metabolism of apolipoprotein B100-containing lipoproteins despite qualitative abnormalities in type 1 diabetic men

Aims/hypothesis Type 1 diabetic subjects are at increased risk of cardiovascular disease and exhibit multiple qualitative abnormalities of apolipoprotein (apo) B100-containing lipoproteins. This stable isotope kinetic experiment was designed to study whether these abnormalities are associated with changes in the synthesis and fractional catabolic rates of VLDL-, IDL- and LDL-apoB100.Methods Using a bolus followed by a 16-h constant infusion of ¹³C-leucine, we performed a kinetic study in eight men with type 1 diabetes treated with a continuous subcutaneous insulin infusion administered by an external pump and in seven healthy men, in the fed state.Results The mean HbA₁c level in the type 1 diabetic patients was 8.00±1.48%. Plasma triglyceride, and total, LDL and HDL cholesterol levels were similar in patients and control subjects. VLDL were less triglyceride rich in type 1 diabetic patients than in control subjects (VLDL triglyceride : apoB 6.91±0.81 vs 8.29±1.24 mmol/g, p=0.05). Conversely, the IDL and LDL of the type 1 diabetic patients contained relatively higher levels of triglycerides (IDL triglycerides : apoB 2.16±0.36 vs 1.57±0.30 mmol/g, p<0.01; LDL triglycerides : apoB 0.27±0.06 vs 0.16±0.04 mmol/g, p<0.05). The apoB100 pool size, production and fractional catabolic rates in the two groups of subjects were similar for all lipoprotein fractions.Conclusions/interpretation Despite qualitative abnormalities, especially abnormalities of triglyceride content, the metabolism of apoB100-containing lipoproteins is not altered in type 1 diabetic men with fair glycaemic control with continuous subcutaneous insulin infusion. The high risk of atherosclerosis in these patients cannot be explained by kinetic abnormalities of apoB100-containing lipoproteins.     

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.     

Lipoprotein analyses in varying degrees of glucose tolerance. Comparison between non-insulin-dependent diabetic, impaired glucose tolerant, and control populations

Atherosclerosis is the major cause of death in diabetic patients. Lipoproteins and lipids are frequently altered in non-insulin-dependent diabetes. These lipoprotein alterations are of interest because of their possible role in the origin of the accelerated atherosclerosis found in diabetes. Because of the link between lipoproteins and diabetes, serum lipids and lipoproteins were measured in 215 middle-aged patients (107 female, 108 male) with varying degrees of glucose tolerance: control subjects, subjects with impaired glucose tolerance (IGT), and patients with non-insulin-dependent diabetes mellitus (NIDDM). In male subjects, levels of fasting total triglycerides were significantly greater in those with NIDDM compared with control subjects. In female subjects, fasting total cholesterol levels were significantly greater in NIDDM compared with IGT. Both high-density lipoprotein (HDL) cholesterol and HDL2 cholesterol values were significantly lower in both sexes with NIDDM compared with control subjects. Low-density lipoprotein (LDL) cholesterol levels were elevated in the male subjects with IGT. No differences in HDL cholesterol or its subfractions were seen in both sexes with IGT compared with control subjects. Bivariate analyses showed that the reduced HDL cholesterol and HDL subfraction levels were most closely associated with both total triglycerides and weight. This study shows that reduced HDL cholesterol and HDL2 cholesterol levels occur in NIDDM, whereas persons with "impaired glucose tolerance" do not have the dramatic alterations in HDL levels.     

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     

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.     

Long-term physical training in female Type 1 (insulin-dependent) diabetic patients: absence of significant effect on glycaemic control and lipoprotein levels

Summary No objective evidence has been presented to support the beneficial effect of physical training on glycaemic control in Type 1 (insulin-dependent) diabetic patients trained two to three times a week for several months. In the present study we examined the possibility that a daily exercise programme would be more suitable for improving glycaemic control. Thirteen patients completed a 5-month study; 6 were randomized to exercise training (20 min daily bicycle exercise) and 7 served as non-exercising controls. The training resulted in an 8% increase in maximal oxygen uptake (p < 0.05). No change in glycaemic control occurred during the study period in either group. In addition, serum lipid and lipoprotein levels were followed. Total cholesterol decreased during the study period irrespective of training. No effect was noted on the levels of LDL, VLDL, HDL and HDL₂ cholesterol. A significant training effect was obtained in the HDL₃ subfraction (−10%,p < 0.05). Total triglycerides were unchanged, but a decrease in the level of LDL triglycerides was observed with training (−12%,p < 0.01). It is concluded that, in female Type 1 diabetic patients, daily physical training for several months does not improve glycaemic control and results only in minor changes in serum lipoprotein profiles.     

Heterogeneity of human high density lipoprotein: Presence of lipoproteins with and without apoE and their roles as substrates for lecithin:cholesterol acyltransferase reaction

By affinity chromatography on heparin-Sepharose, two classes of lipoproteins were separated from high density lipoproteins (HDL) isolated from patients with primary or secondary lecithin:cholesterol acyltransferase (LCATase; EC 2.3.1.43) deficiency and from normal subjects. The unretained fraction, HDL_A, was characterized by having apoA-I as a major apoprotein; it also contained apoA-II, -C-II, and -C-III but it contained only traces of immunodetectable apoE and no apoB. The retained fraction, HDL_E, had apoE as the major apoprotein; it also contained apoA-I, -A-II, -B, -C-II, and -C-III. The relative concentration of apoA-I increased with increasing density in the HDL_E subclass. Compared to HDL_A, HDL_E had a significantly higher cholesterol content and a lower protein concentration. HDL_E was mainly (90%) contained within the HDL₂ subfraction. Contamination of HDL_E by low density lipoproteins (LDL) or Lp(a) was minimal on the basis of pre-β-electrophoretic mobility and absence of albumin, respectively. Contamination by LDL or Lp(a) could be resolved in part by application of HDL_E to concanavalin A-Sepharose or to heparin-Sepharose with a shallow gradient. When evaluated as substrates for a highly purified LCATase preparation, the initial reaction rates and V_max obtained with HDL_A were always higher than those obtained with HDL_E in any given plasma. However, both HDL subclasses from LCATase-deficient subjects were better substrates than the corresponding HDL subclasses from normal plasma. Also, both HDL_3A and HDL_3E isolated from normal HDL₃ were better substrates than the corresponding subclasses isolated from normal HDL₂. The recognition of this compositional and functional heterogeneity within HDL will allow a better understanding of the metabolism of this lipoprotein class.     

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     

Effect of simvastatin on high density lipoprotein subfractions and apolipoproteins in Type IIa hypercholesterolemia

Summary Changes in plasma concentrations of high density lipoproteins (HDL) and triglycerides may partly explain the ability of cholesterol-lowering drugs to decrease the incidence of coronary heart disease. We measured the response of fasting plasma lipids, lipoproteins, and apolipoproteins in 46 subjects with Type IIa hypercholesterolemia treated with simvastatin for 3 months. The initial dose of simvastatin (10 mg/day) was subsequently increased up to 40 mg/day if the plasma cholesterol concentration had not fallen below 5.2 mmol/l. Plasma concentrations of HDL cholesterol and of the apolipoproteins AI and AII were increased by simvastatin. The increase in HDL cholesterol (9%) was due to increases in both subfractions (HDL₂ 17%; HDL₃ 7%), changes that would be consistent with a beneficial effect on cardiovascular risk. Simvastatin decreased plasma triglyceride concentrations by 25%. Plasma total cholesterol concentrations fell by 35% after 3 months of treatment; this fall was proportional to the initial concentration and was due almost entirely to a 45% fall in low density lipoprotein cholesterol. In contrast, plasma concentrations of lipoprotein Lp(a) were not affected by simvastatin.     

Plasma adiponectin is associated with less atherogenic lipoprotein phenotype

Background and aims

This study examined the relationships between plasma levels of adiponectin and the features of the atherogenic lipoprotein phenotype (ALP), including HDL subclasses.

Methods and results

Blood lipids and apolipoproteins were measured in 293 healthy individuals. LDL particle size and HDL subspecies (HDL₂, HDL₃) were measured using gradient gel electrophoresis. Plasma adiponectin levels were negatively correlated with levels of apoB (r = −0.199, p < 0.001), TG (r = −0.262, p < 0.001), and HOMA-IR (r = −0.323, p < 0.001) and positively correlated with levels of apoAI (r = 0.173, p = 0.006), HDL-cholesterol (r = 0.287, p < 0.001), and LDL particle size (r = 0.289, p < 0.001). Multiple linear regression analysis revealed the relationship between plasma adiponectin and LDL particle size (p < 0.05) was no longer significant after adjusting for plasma TG levels. However, adiponectin (p < 0.005) together with apoAI and TG were independent factors for HDL-cholesterol. With regard to HDL subclasses, plasma adiponectin levels were positively correlated with HDL_2b (r = 0.204, p < 0.001), HDL_2a (r = 0.132, p < 0.05) and negatively with HDL_3a (r = −0.128, p < 0.05), HDL_3b (r = −0.203, p < 0.001), and HDL_3c (r = −0.159, p < 0.01). The relationship between circulating adiponectin and HDL₂ (HDL_2b + HDL_2a) was independent of apoB and TG levels (p < 0.05), but not of apoAI and HOMA-IR.

Conclusions

Our results show that circulating adiponectin is associated with reduced manifestations of ALP.     

Cholesterol Rich apo B Containing Lipoproteins and Smoking are Independently Associated with Macrovascular Disease in Normotensive NIDDM Patients

A cross-sectional study of macrovascular disease (MVD) and associated metabolic and other risk factors was conducted in 87 normotensive NIDDM patients. MVD was assessed by Rose questionnaire, 12 lead resting ECG, duplex scanning of carotid and peripheral vessels, and ankle:brachial systolic blood pressure ratio. Fasting serum total cholesterol, total triglycerides, LDL cholesterol, HDL cholesterol, apolipoproteins AI and B, lipoprotein (a), HbA₁, plasma glucose, insulin, and C-peptide responses to a carbohydrate rich meal, body mass index (BMI), waist-hip ratio, urinary albumin excretion rate, blood pressure, smoking and family history were assessed as possible ‘risk factors’. Apolipoprotein:lipid ratios were calculated to estimate lipoprotein composition. Thirty-six patients had demonstrable MVD. The presence of MVD was associated with higher total triglycerides (p < 0.05), BMI (p < 0.05), systolic blood pressure (p < 0.01), a lower apo B:non HDL cholesterol ratio (p < 0.001), and smoking (p < 0.005) but no other measures. Multiple regression analysis revealed smoking and a low apo B:non HDL cholesterol to be independently associated with MVD. The low apo B:non HDL cholesterol suggests a high cholesterol content of apo B containing lipoproteins. This lipoprotein abnormality is not a feature of NIDDM, but when present in these patients may be particularly atherogenic.     

Treatment of dyslipidemia in non-insulin-dependent diabetes mellitus with lovastatin

Coronary artery disease (CAD) is the leading cause of death among whites with non-insulin-dependent diabetes mellitus (NIDDM). Several risk factors--dyslipidemia induced by NIDDM, obesity, hypertension and hyperglycemia--likely contribute to accelerated atherosclerosis. The dyslipidemia in NIDDM is characterized by abnormalities in composition and metabolism of very low density lipoproteins, low-density lipoproteins (LDL) and high-density lipoproteins (HDL). However, because of the lack of long-term prospective epidemiologic studies, the relative importance of lipoprotein risk factors in the causation of CAD in diabetic patients is not clear. The World Health Organization Multinational Study of vascular disease in diabetics observed increased prevalence of CAD in diabetic populations with relatively high levels of plasma cholesterol and supports the concept that lowering cholesterol levels may significantly reduce coronary risk in NIDDM. To determine the effectiveness of lovastatin, an inhibitor of HMG CoA reductase, for lowering cholesterol levels, 16 patients with NIDDM and mild to moderate increases in plasma cholesterol were given lovastatin (20 mg twice daily) in a randomized, double-blind, placebo-controlled manner for 4 weeks. Compared with the placebo, lovastatin reduced concentrations of total cholesterol (233 +/- 10 vs 172 +/- 7 mg/dl [standard error of the mean], p less than 0.001), LDL cholesterol (140 +/- 9 vs 101 +/- 6 mg/dl, p less than 0.001), and LDL apolipoprotein-B (108 +/- 16 vs 80 +/- 16 mg/dl, p less than 0.001). Plasma triglycerides and very low density lipoprotein cholesterol levels also decreased by 31 and 42%, respectively. Although HDL cholesterol levels did not increase, the total cholesterol/HDL cholesterol ratio decreased significantly with lovastatin therapy. No adverse effects were noted and glycemic control was well-maintained.(ABSTRACT TRUNCATED AT 250 WORDS)