Presence of very low density lipoprotein compositional abnormalities in Type 1 (insulin-dependent) diabetic patients; effects of blood glucose optimisation

Summary Plasma lipoprotein compositional abnormalities were investigated in eight normolipidaemic (plasma cholesterol <5.70 mmol/l; triglyceride <2.03 mmol/l) young male Type 1 (insulin-dependent) diabetic patients (before and after a short period of optimised blood glucose control) and in nine healthy control subjects, matched for sex, age and body mass index. Free and esterified cholesterol, triglyceride, phospholipids were assayed in all lipoprotein classes (VLDL, IDL, LDL) and in HDL subclasses (HDL2 and HDL3); apoB was measured only in very low density lipoproteins (VLDL). All VLDL constituents were increased in the diabetic group, the differences being more striking for apoB (6.0±1.1 mg/dl vs 2.0±0.1 mg/dl, p<0.02), free cholesterol (0.27±0.04 mmol/l vs 0.13±0.02 mmol/l, p<0.02) and esterified cholesterol (0.32±0.08 mmol/l vs 0.13±0.01 mmol/l, p<0.05). Also HDL subfractions showed differences between the two groups: all HDL2 constituents were increased, while in HDL3 only triglyceride was significantly increased (0.11±0.01 mmol/l vs 0.08±0.004 mmol/l, p<0.02). After two weeks of optimised blood glucose control all VLDL constituents were reduced and particularly: esterified cholesterol (–39%, p<0.02), free cholesterol (–37%, p<0.05), apoB (– 35%, p<0.05). Expressing each VLDL constituent as percent of the total lipoprotein mass, it was evident that the diabetic VLDL was rich in cholesterol both esterified (8.4±1.0% vs 5.4±0.5%, p<0.02) and free (8.5±0.7% vs 5.5±0.3%, p<0.001), apo B (5.1±0.6% vs 2.6±0.3%, p<0.001) and depleted in triglyceride (57.0±1.7% vs 64.1±1.7%, p<0.001). Two weeks of optimised blood glucose control were not able to correct the abnormal composition of VLDL. In conclusion, Type 1 (insulin-dependent) diabetic patients, although normolipidaemic, show an abnormal VLDL composition suggesting an increased prevalence of smaller and, possibly, more atherogenic VLDL particles. This abnormality is not corrected by a short period of blood glucose optimisation.     

Changes of lipolytic enzymes cluster with insulin resistance syndrome

Summary The activities of hepatic and lipoprotein lipase and the levels of lipo- and apoproteins were compared in two groups of normoglycaemic men representing the highest (n=18) and lowest (n=15) fasting insulin quintiles of first degree male relatives of non-insulin-dependent diabetic patients. The high insulin group representing insulin-resistant individuals had significantly lower post-heparin plasma lipoprotein lipase activity than the low insulin group (14.2±4.0 vs 20±5.8 mol NEFA·ml^–1·h^–1, p<0.001); hepatic lipase activity did not differ between the two groups (24.2±11 vs 18.0±5.3 mol NEFA·ml^–1·h^–1, NS). The lipoprotein lipase/hepatic lipase ratio in the high insulin group was decreased by 66% as compared to the low insulin group (0.75±0.57 vs 1.25±0.65, p<0.01). In the high insulin group both total and VLDL triglycerides were higher than in the low insulin group (1.61±0.57 vs 0.86±0.26 mmol/l, p< 0.001 and 1.00±0.47 vs 0.36±0.16 mmol/l, p<0.001, respectively) whereas HDL cholesterol and HDL₂ cholesterol were lower (1.20±0.30 vs 1.43±0.22 mmol/l, p<0.05 and 0.49±0.21 vs 0.71±0.17 mmol/l, p<0.05, respectively). Total cholesterol, LDL cholesterol or HDL₃ cholesterol did not differ between the two groups. The mean particle size of LDL was smaller in the high insulin group than in the low insulin group (258±7 vs 265±6 å, p<0.05). We propose that the changes of lipoprotein lipase and lipoprotein lipase/hepatic lipase ratio cluster with insulin resistance and provide a possible mechanism to explain the lowering of HDL cholesterol and elevation of triglyceride concentrations observed in insulin-resistant subjects.Abbreviations LPL Lipoprotein lipase - HL hepatic lipase - VLDL very low density lipoprotein - IDL intermediate density lipoprotein - LDL low density lipoprotein - HDL high density lipoprotein - chol cholesterol - TG triglycerides - NEFA non-esterified fatty acids     

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.     

Inability of HDL from type 2 diabetic patients to counteract the inhibitory effect of oxidised LDL on endothelium-dependent vasorelaxation

Aims/hypothesis In healthy normolipidaemic and normoglycaemic control subjects, HDL are able to reverse the inhibition of vasodilation that is induced by oxidised LDL. In type 2 diabetic patients, HDL are glycated and more triglyceride-rich than in control subjects. These alterations are likely to modify the capacity of HDL to reverse the inhibition of vasodilation induced by oxidised LDL.Subjects and methods Using rabbit aorta rings, we compared the ability of HDL from 16 type 2 diabetic patients and 13 control subjects to suppress the inhibition of vasodilation that is induced by oxidised LDL.Results Oxidised LDL inhibited endothelium-dependent vasodilation (maximal relaxation [Emax]=58.2±14.6 vs 99.3±5.2% for incubation without any lipoprotein, p<0.0001). HDL from control subjects significantly reduced the inhibitory effect of oxidised LDL on vasodilatation (Emax=77.6±12.9 vs 59.5±7.7%, p<0.001), whereas HDL from type 2 diabetic patients had no effect (Emax=52.4±20.4 vs 57.2±18.7%, NS). HDL triglyceride content was significantly higher in type 2 diabetic patients than in control subjects (5.3±2.2 vs 3.1±1.4%, p<0.01) and was highly inversely correlated to Emax for oxidised LDL+HDL in type 2 diabetic patients (r=−0.71, p<0.005).Conclusions/interpretation In type 2 diabetes mellitus, the ability of HDL to counteract the inhibition of endothelium-dependent vasorelaxation induced by oxidised LDL is impaired and is inversely correlated with HDL triglyceride content. These findings suggest that HDL are less atheroprotective in type 2 diabetic patients than in control subjects.     

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     

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     

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)     

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.     

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.     

Low HDL‐cholesterol is common in European Type 2 diabetic patients receiving treatment for dyslipidaemia: data from a pan‐European survey

Aims To measure the prevalence of low high‐density lipoprotein (HDL)‐cholesterol (men < 1.03 mmol/l; women < 1.29 mmol/l) in European Type 2 diabetic patients receiving treatment for dyslipidaemia. Methods The pan‐European Survey of HDL‐cholesterol measured lipids and other cardiovascular risk factors in 3866 patients with Type 2 diabetes and 4436 non‐diabetic patients undergoing treatment for dyslipidaemia in 11 European countries. Results Diabetic patients were more likely to be obese or hypertensive than non‐diabetic patients. Most patients received lifestyle interventions (87%) and/or a statin (89%); treatment patterns were similar between groups. Diabetic patients had [means (SD)] lower HDL‐cholesterol [1.22 (0.37) vs. 1.35 mmol/l (0.44) vs. non‐diabetic patients, P < 0.001] and higher triglycerides [2.32 (2.10) vs. 1.85 mmol/l (1.60), P < 0.001]. More diabetic vs. non‐diabetic patients had low HDL‐cholesterol (45% vs. 30%), high triglycerides (≥ 1.7 mmol/l; 57% vs. 42%) or both (32% vs. 19%). HDL‐cholesterol < 0.9 mmol/l was observed in 18% of diabetic and 12% of non‐diabetic subjects. Differences between diabetic and non‐diabetic groups were slightly greater for women. LDL‐ and total cholesterol were lower in the diabetic group [3.02 (1.05) vs. 3.30 mmol/l (1.14) and 5.12 (1.32) vs. 5.38 mmol/l (1.34), respectively, P < 0.001 for each]. Conclusions Low HDL‐cholesterol is common in diabetes: one in two diabetic women has low HDL‐cholesterol and one diabetic man in four has very low HDL‐cholesterol. Management strategies should include correction of low HDL‐cholesterol to optimize cardiovascular risk in diabetes.     

Response of adipose tissue lipoprotein lipase activity and serum lipoproteins to acute hyperinsulinaemia in man

Summary In order to assess the short-term effects of hyperinsulinaemia and hyperglycaemia on adipose tissue lipoprotein lipase activity and on serum lipoproteins, we measured these variables in ten normal subjects during euglycaemic and hyperglycaemic hyperinsulinaemic clamps. The mean steady-state plasma glucose and insulin concentrations, respectively, were 4.7 mmol/l and 101 mU/l during euglycaemic moderate-insulin clamp, 4.9 mmol/l and 565 mU/l during euglycaemic high-insulin clamp, and 8.8 mmol/l and 148 mU/l during hyperglycaemic clamp. Saline infusion was used as control. The adipose tissue lipoprotein lipase activity rose significantly over 5 h during high-insulin clamp (p<0.01) and during hyperglycaemic clamp (p<0.05), but did not change during the moderate-insulin clamp. The magnitude of change of lipoprotein lipase activity from baseline (either rise or fall) was inversely related to the preclamp activity during euglycaemic moderate-insulin clamp (r= -0.67), during hyperglycaemic clamp (r= -0.68) and during infusion of saline (r= -0.75, p<0.05). Total serum triglyceride concentration decreased significantly during all clamp studies compared with the control experiment. This change was mainly accounted for by a decrease of VLDL triglyceride. The LDL cholesterol level fell by an average of 5% (p<0.05) during the high-insulin clamp and by 10% (p<0.05) during the hyperglycaemic clamp. The HDL cholesterol level did not change significantly. It is concluded that adipose tissue lipoprotein lipase activity in man is increased by physiological insulin levels during hyperglycaemia and also by supraphysiological insulin levels during euglycaemia, but is not influenced by physiological hyperinsulinaemia without hyperglycaemia. Low basal lipoprotein lipase activity is more sensitive to insulin-glucose stimulation than primarily high lipoprotein lipase activity. Acute hyperinsulinaemia decreases VLDL triglyceride and LDL cholesterol concentrations.     

Effects of dietary cholesterol on plasma lipoproteins and their subclasses in IDDM patients

Summary To compare the effects of dietary cholesterol supplementation in insulin-dependent diabetic (IDDM) patients and normal subjects, 10 male IDDM patients in good glycaemic control (HbA_{1 c} 7.3 ± 0.9 %) (mean ± SD) and normal plasma lipid levels, and 11 control male subjects of similar age, body mass index and lipid plasma levels underwent a double blind, cross-over, sequential study. Cholesterol supplementation of 800 mg/day or placebo were given for consecutive periods of 3 weeks. The concentration of plasma total cholesterol increased significantly with the dietary cholesterol supplementation compared to placebo in IDDM patients by 6 % (p < 0.05) and in control subjects by 9 % (p < 0.05). No changes were observed in the concentration of plasma triglycerides in either group. The LDL cholesterol level increased by 12 % (p < 0.01) in patients and by 7 % (p < 0.05) in control subjects. In patients plasma HDL cholesterol concentration remained the same, while in control subjects it tended to increase after cholesterol supplementation (from 1.14 ± 0.26 to 1.23 ± 0.27 mmol/l, p = 0.06). During the cholesterol intake period the mean concentration of LDL1, LDL2 and LDL3 subclasses in patients showed a significant increase by 21.0 (p < 0.05), 20.4 (p < 0.001) and 11.1 % (p < 0.05), respectively, resulting in an 18.0 % increase in mean total LDL mass (p < 0.001) without major changes in LDL composition. In the control subjects the changes in the concentrations of LDL subclasses during cholesterol intake were less and not significant. In the IDDM patients the cholesterol intake did not affect the concentration or composition of HDL subclasses or total HDL mass. In contrast, in control subjects cholesterol intake increased the mean concentration of HDL2 a by 12.2.% (p < 0.05) and this increase was significantly different if compared to changes obtained in the patients. In conclusion, compared to normal subjects, in IDDM patients, dietary cholesterol intake increased the LDL particle mass significantly and had no positive effect on HDL. [Diabetologia (1998) 41: 193–200] Received: 4 July 1997 and in revised form: 12 September 1997     

Elevated serum lipoprotein(a) in subclinical hypothyroidism

OBJECTIVES Asymptomatic lymphocytic thyroiditis and subclinical hypothyroidism are associated with increased risk for coronary artery disease. The present study aimed at evaluating serum lipoprotein(a)(Lp(a), measured as apo(a), and other lipid parameters In 32 subjects with asymptomatic subclinical hypothyroidism. SUBJECTS Thirty-two Chinese subjects with asymptomatic subclinical hypothyroidism were compared to 96 age and sex-matched healthy controls. RESULTS Subclinical hypothyroid patients had higher (P < 0.005) apo(a), total triglyceride (TG), total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) but lower (P < 0.05) high density lipoprotein cholesterol (HDL-C) levels compared with sex and age-matched controls (apo(a) 296 (48–1650) vs 182 (19–1952 U/I), geometric mean (range); TG 1.86 ± 0.94 vs 1.33±0.74mmol/l (mean ± SD); TC 6.10 ±1.17 vs 5.42 ±1.13 mmol/l; LDL-C 410 ± 1.00 vs 3.49 ± 0.96 mmol/l; HDL-C 1.15 ± 0.40 vs 1.34 ± 0.40 mmol/l, respectlvely). Apo A-I and apo B were also higher than controls (1.96 ± 048 vs 1.48 ± 029 g/l and 1.44 ± 042 vs 1.05±029 g/l, respectively). Total cholesterol/HDL ratio and LDL/HDL ratio were also elevated in these subjects (577 ± 1.96 vs 428 ±1.19 and 389 ± 1.41 vs 2.79 ± 0.97, respectively, both P < 0.0005). Individual analysis revealed that 16 (50%) subjects had hyperlipoprotelnaemia (TC > 5.2 mmol/l in 10;TC > 52 mmol/l and TG > 2.3mmol in six) as compared to 21(208%) in the control group (P < 0.005). Subjects with TSH ± 11.0mlU/l had significantly higher TC/HDL and LDL/HDL ratios. A significant correlation was observed between TSH levels and TC/HDL ratios (r = 0.455, P < 001). CONCLUSIONS Subclinical hypothyroidism Is associated not only with elevated LDL-cholesterol levels and low HDL-cholesterol levels but also with elevated lipoprotein (a). This may further Increase the risk development of atheroscierosis.     

Effect of cranberry extracts on lipid profiles in subjects with Type 2 diabetes

Aim To examine the effect of cranberry ingestion on lipid profiles in Type 2 diabetic patients taking oral glucose‐lowering drugs. Methods Thirty Type 2 diabetic subjects (16 males and 14 females; mean age 65 ± 1 years) who were taking oral glucose‐lowering medication regularly were enrolled in this randomized, placebo‐controlled, double‐blind study. Changes in lipid profiles, oxidized low‐density lipoprotein (ox‐LDL), glycaemic control, components of the metabolic syndrome, C‐reactive protein (CRP) and urinary albumin excretion (UAE) were assessed after cranberry or placebo treatment for 12 weeks. Results Low‐density lipoprotein (LDL) cholesterol decreased significantly in the cranberry group (from 3.3 ± 0.2 to 2.9 ± 0.2 mmol/l, P = 0.005) and the decrease was significantly greater than that in the placebo group (–0.4 ± 0.1 vs. 0.2 ± 0.1 mmol/l, P < 0.001). Total cholesterol and total : high‐density lipoprotein (HDL) cholesterol ratio also decreased significantly (P = 0.020 and 0.044, respectively) in the cranberry group and the reductions were significantly different from those in the placebo group (P < 0.001 and P = 0.032, respectively). However, ox‐LDL levels did not change significantly in response to cranberry consumption. Neither fasting glucose nor glycated haemoglobin improved in either group. Changes in components of the metabolic syndrome, UAE and CRP were not significantly different between groups. Conclusions Cranberry supplements are effective in reducing atherosclerotic cholesterol profiles, including LDL cholesterol and total cholesterol levels, as well as total : HDL cholesterol ratio, and have a neutral effect on glycaemic control in Type 2 diabetic subjects taking oral glucose‐lowering agents.     

Elevated serum levels of<Emphasis Type="Italic"> N</Emphasis><Superscript>ε</Superscript>-carboxymethyl-lysine,an advanced glycation end product,are associated with proliferative diabetic retinopathy and macular oedema

Aims/hypothesis Diabetic retinopathy is a frequent microvascular complication. In search of novel risk markers, we analysed the association between serum levels of the major advanced glycation end product N-carboxymethyl-lysine (CML) and prevalence of advanced stages of retinopathy in Type 2 diabetic patients without nephropathy.Methods We carried out a case-control study of Type 2 diabetic patients with and without advanced stages of diabetic retinopathy. Retinopathy and macular oedema were defined according to standard criteria. Serum levels of CML were estimated by means of a novel competition-based ELISA assay.Results Serum levels of CML were significantly different between age-matched controls (n=792; mean value ± SD: 521±134 ng/ml), Type 2 diabetic patients without severe retinopathy (821±141 ng/ml; p<0.0001) and Type 2 diabetic patients with proliferative retinopathy (1182±346 ng/ml; p<0.0001). Levels of CML greater than 1000 ng/ml represented a 25-fold increase in risk of proliferative retinopathy. Receiver operating characteristics analysis revealed a CML threshold of 1087 ng/ml (100% sensitivity, 93% specificity) for clinically significant macular oedema.Conclusions/interpretation High serum levels of CML were associated with advanced stages of retinopathy. Serum levels were shown to be a progressive risk marker, whereby a level of more than 1000 ng/ml induced a 25-fold increase in risk of proliferative retinopathy and clinically significant macular oedema. Our data suggest that serum levels of CML provide a novel risk marker for advanced stages of diabetic retinopathy in Type 2 diabetic patients.Abbreviations CML N-carboxymethyl-lysine - ETDRS Early Treatment Diabetic Retinopathy Study - RAGE receptor for advanced glycation end products - ROC receiver operating characteristics     

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     

Oxidation of low-density lipoprotein in NIDDM: its relationship to fatty acid composition

Summary The increased risk of atherosclerotic disease in diabetic subjects may be due to enhanced foam cell formation following an increased susceptibility of low density lipoprotein to oxidative modification. This study has compared fatty acid content and lipoprotein oxidisability in 10 non-insulin-dependent diabetic subjects with that in 10 control subjects. Both groups were normocholesterolaemic and the diabetic subjects had higher triglyceride levels (2.2±0.4 vs 1.2±0.2 mmol/l, p<0.05). The fatty acid composition was compared in low density lipoprotein following Folch extraction, separation by thin layer chromatography (for the lipid classes) and analysis by gas liquid chromatography. Low density lipoprotein oxidisability was assessed by conjugated diene and thiobarbituric acid reacting substance formation in the presence of copper ions. The esterified/free cholesterol ratio was higher in the low density lipoprotein from patients compared to control subjects (2.9±0.1 vs 1.9±0.3, p<0.05). Linoleic acid in the cholesteryl ester fraction of the lipoprotein was higher in the patients than in the control subjects (48.2±2.2% vs 42.4±3.4%, p<0.05) as was the total quantity of linoleic acid in the cholesteryl ester fraction (317.8±68.0 vs 213.2±28.0 g/mg protein, p<0.05) and in the low-density lipoprotein as a whole (443.2±70.0 vs 340.2±28.2 g/mg protein, p<0.05). Lipoprotein oxidisability was also increased in the diabetic group with increased formation of thiobarbituric acid reacting substances (35.6±7.2 vs 22.3±3.5 nmol/mg protein, p<0.05, increased total diene formation (502±60 vs 400±30 nmol/mg protein, p<0.05) and increased rate of diene formation (7.2±0.6 vs 5.1±0.9 nmol diene · mg protein^–1 · min^–1, p<0.05). This study indicates that low-density lipoprotein from diabetic subjects is more susceptible to oxidation. This could, in vivo, accelerate foam-cell formation thereby increasing atherosclerotic risk in diabetic subjects.Abbreviations BHT Butylated hydroxytoluene - EDTA ethylenediaminetetraacetic acid - TBARS thiobarbituric reacting substances - HPLC high performance liquid chromatography - MDA malondialdehyde - HbA_1c glycated haemoglobin     

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.     

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.     

Raised serum apolipoprotein (a) in active diabetic retinopathy

Summary Progressive capillary occlusion often leads to severe retinopathy within 15–20 years of the onset of Type 1 (insulin-dependent) diabetes mellitus. Lipoprotein (a), a complex formed by apolipoprotein (a), apo B-100 and lipids, is considered an independent, genetically determined, predictor of cardiovascular disease. It may have antifibrinolytic properties in view of its similarity to plasminogen. To test the hypothesis that circulating lipoprotein (a) is associated with the process that leads to clinically active diabetic retinopathy, we measured the circulating levels of apolipoprotein (a) (which are strictly correlated with those of lipoprotein (a)) in two groups of patients with Type 1 diabetes of at least 15 years duration: 25 with active retinopathy and 27 without clinically detectable retinal lesions. Thirty-eight healthy subjects of the same age and sex served as controls. Serum apolipoprotein (a) was higher in the patients with active retinopathy (36(2-193) U/dl, geometric mean and range) than in those without clinically detectable retinal lesion (17(1–160)) and the control subjects (14(0–115)), p < 0.01 in both cases. The distribution of apolipoprotein (a) levels was skewed to the left, as expected, in the patients without clinically evident retinal lesions and the control groups, but there was a bimodal trend of distribution among those with active retinopathy. The levels of glycated haemoglobin were similar in the two groups of diabetic patients, and no significant differences were found for total and HDL cholesterol, triglycerides or apolipoproteins A1 and B between them and the control subjects. These preliminary results suggest that serum apolipoprotein (a) is elevated in patients with active retinopathy. The role of this lipoprotein as a predictor or a pathogenic effector of diabetic retinopathy, or both deserves further investigation.