Lack of change of lipoprotein (a) concentration with improved glycemic control in subjects with type II diabetes

Lipoprotein (a): impact by ethnicity and environmental and medical conditions

Levels of lipoprotein (a) [Lp(a)], a complex between an LDL-like lipid moiety containing one copy of apoB, and apo(a), a plasminogen-derived carbohydrate-rich hydrophilic protein, are primarily genetically regulated. Although stable intra-individually, Lp(a) levels have a skewed distribution inter-individually and are strongly impacted by a size polymorphism of the LPA gene, resulting in a variable number of kringle IV (KIV) units, a key motif of apo(a). The variation in KIV units is a strong predictor of plasma Lp(a) levels resulting in stable plasma levels across the lifespan. Studies have demonstrated pronounced differences across ethnicities with regard to Lp(a) levels and some of this difference, but not all of it, can be explained by genetic variations across ethnic groups. Increasing evidence suggests that age, sex, and hormonal impact may have a modest modulatory influence on Lp(a) levels. Among clinical conditions, Lp(a) levels are reported to be affected by kidney and liver diseases.

Lipoprotein (a) in type 2 diabetes mellitus: Relation to LDL:HDL ratio and glycemic control

BACKGROUND

Increased lipoprotein (a) [Lp (a)] concentrations are predictive of coronary artery disease (CAD). Type 2 diabetes mellitus also leads to dyslipidemia, like elevated triglyceride levels and low HDL levels, which are known risk factors for CAD. This study was designed to investigate the levels of Lp (a) in type 2 diabetic patients and their association with LDL: HDL ratio and glycemic control.

MATERIALS AND METHODS

The study included 60 patients of type 2 diabetes and 50 age and sex matched controls. The Lp(a) levels in the diabetic group were compared with the control group and the relationship between the Lp(a) levels and LDL: HDL ratio was evaluated. Diabetic group was further divided into three subgroups according to levels of glycated hemoglobin. Lp(a) levels and glycated hemoglobin in controlled and uncontrolled diabetes mellitus were also compared to find out any correlation between them. Statistical analysis was done using the students 't' test and Chi square test.

RESULTS

Lp(a) levels were found to be significantly increased in the diabetic group as compared to the control group (P< 0.001). LDL: HDL ratio was also increased in the diabetic group as compared to the control group. Lp(a) levels showed no association with LDL: HDL ratio and degree of glycemic control in these patients.

CONCLUSIONS

The results of the present study suggest that Lp(a) levels are increased in type 2 diabetic patients. The elevated Lp(a) levels do not reflect the glycemic status and are also independent of increase in LDL:HDL ratio suggesting different metabolic pathways and the genetic connection for LDL and Lp(a).

Pathogenesis and management of diabetic dyslipidemia

Patients with diabetes mellitus have a 2- to 4-fold increased risk of atherosclerotic cardiovascular, peripheral vascular, and cerebrovascular disease, which are the leading causes of morbidity and mortality in this population. Several epidemiological studies have shown an association between diabetic dyslipidemia, which is characterized by hypertriglyceridemia, low levels of high density lipoprotein-cholesterol, postprandial lipemia and small, dense low density lipoprotein-cholesterol (LDL-C) particles, and the occurrence of cardiovascular disease. Other studies have established the beneficial effects of lipid lowering on the reduction of major coronary events in diabetic patients. The recent National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) guidelines emphasize diabetes as a coronary heart disease risk equivalent. The NCEP ATP III states that elevated LDL-C is a major risk factor for coronary heart disease, and the primary goal of risk-reduction therapy is the reduction of LDL-C levels to 100 mg/dL. This article defines and describes diabetic dyslipidemia and its etiology and pathogenesis, as well as reviewing guidelines and recommendations for treatment of this disorder. Treatment of diabetic dyslipidemia includes 1) lifestyle modifications: physical activity and a diet low in saturated fats and cholesterol and high in complex carbohydrates and fiber; and 2) pharmacological treatment with (i) oral antihyperglycemic agents: metformin and thiazolidinediones; (ii) weight reduction drugs: orlistat and sibutramine and; (iii) lipid-lowering drugs: HMG-CoA reductase inhibitors, fibric acid derivatives, nicotinic acid, and bile acid sequestrants.

Test and teach. Number Fifty-three. Diagnosis: Diabetes-related dyslipidaemia

Mixed dyslipidaemia is common in people with diabetes and occurs in up to 20% of cases. Diabetes keto-acidosis can occur in patients with type 2 diabetes. Hypertriglyceridaemia is a well-recognised cause of pancreatitis. Other common causes of pancreatitis include gall stones, alcohol, drugs (azathioprine and dideoxyinosine) and post-endoscopic retrograde cholangiopancreatography (ERCP). Therapeutic options for acute and severe dyslipidaemia include insulin therapy, fibric acid derivatives, fish oils and, rarely, nicotinic acids. Hospitalisation may be required for plasmapheresis in specialised centres.

Lipoprotein(a) in patients who have non-insulin-dependent diabetes with and without coronary artery disease

OBJECTIVE

To determine whether the level of lipoprotein(a) [Lp(a)] contributes to an increased risk of coronary artery disease (CAD) in patients with non-insulin-dependent diabetes mellitus (NIDDM).

METHODS

We prospectively evaluated established cardiovascular risk factors, metabolic control, and Lp(a) levels in 53 men with NIDDM and CAD and compared these variables in 42 male patients with NIDDM but without CAD.

RESULTS

The groups were comparable for age, diabetes control, treatment and duration of diabetes, obesity, and other cardiac risk factors. Lp(a) levels did not differ between the groups (12.2 versus 12.4 mg/dL in those with and without CAD, respectively) and were unrelated to age, duration of diabetes, diabetes control, obesity, smoking, hypertension, urinary albumin, cholesterol, triglycerides, or high-density lipoprotein cholesterol. Patients with retinopathy had a higher Lp(a) concentration than did those without retinopathy (24.9 +/- 6.0 versus 10.1 +/- 1.5 mg/dL; P = 0.01). A significant correlation existed between Lp(a) and low-density lipoprotein cholesterol concentrations (P = 0.01).

CONCLUSION

Routine measurement of Lp(a) level in patients with NIDDM does not seem warranted because no association was found between Lp(a) concentration and CAD in this study population.

Apoprotein(a) phenotypes and plasma lipoprotein(a) concentration in patients with diabetes mellitus

OBJECTIVES

To determine whether apo(a) isoforms and plasma Lp(a) concentrations in association with some lipid parameters increase the relative risk for the development of atherosclerosis in patients with diabetes mellitus (IDDM and NIDDM).

DESIGN AND METHODS

Apo (a) isoforms, Lp(a) and plasma lipids were determined in 40 IDDM and 65 NIDDM patients and in 182 healthy individuals. Apo(a) isoforms were separated by 3 to 15% gradient SDS-PAGE followed by immunoblotting.

RESULTS

Logistical analysis showed that: Lp(a) levels >30 mg/dL (RR = 0.25, p < 0.000001; RR = 0.18, p < 0.00002), HTA (RR = 0.212, p < 0.00001; RR = 0.30, p < 0.00001), LMW-S1 apo(a) isoform (RR = 6.86, p < 0.0131; RR = 7.04, p < 0.0057) play a significant role in aterogenecity in both groups of patients with DM (IDDM and NIDDM). The 6.50-fold increase in risk was found in NIDDM patients with high Lp(a) levels (>30 mg/dL) and plasma total/HDL cholesterol ratio (4.5-5.8).

CONCLUSION

Elevated Lp(a) levels, LMW S1 apo(a) isoform, HTA and combination of increased Lp(a) levels and total/HDL cholesterol ratio increase the risk for the development of atherosclerosis in patients with DM (IDDM and NIDDM).

Biological variation of lipoprotein(a) in a diabetic population. Analysis of the causes and clinical implications

The aims of the present study were to evaluate the biological variability of lipoprotein(a) (Lp(a)) in diabetic patients and to investigate the biological sources of this variability. Lp(a) was measured by ELISA in four serum specimens collected in 3-month intervals from 70 patients. The other parameters analyzed were: total cholesterol, high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), triglycerides, glucose, HbA and albumin excretion rate. The overall biological within-subject variance (CVb) was 31.7%, and it was inversely correlated with Lp(a) serum levels. According to the initial ranges of Lp(a) serum levels (< 15, 15-30 and > 30 mg/dl) the CVb were 42.3%, 24.1% and 23.7%, respectively. In multivariate analysis the total intra-individual coefficient of variation (CVt) of triglycerides and the CVt of the albumin excretion rate (AER) were independently associated with the CVb of Lp(a) (R2 = 0.54). The intra-individual biological variation of Lp(a) produced a misclassification of 20% of diabetic patients for cardiovascular risk attributable to this lipoprotein. In conclusion, the higher biological variability of Lp(a) observed in diabetic patients suggests that a single determination could be inaccurate to assess the cardiovascular risk associated with this lipoprotein, at least in those patients in whom serum levels are near the cut-off considered as risk for cardiovascular disease (> 30 mg/dl). Finally, triglycerides and AER are the main factors influencing Lp(a) serum levels in the diabetic population.

The effect of rosiglitazone on serum lipoprotein(a) levels in Korean patients with type 2 diabetes mellitus

The aim of the study was to determine if rosiglitazone increases serum levels of lipoprotein(a) [Lp(a)] in Korean patients with type 2 diabetes mellitus. A total of 118 patients were divided into 2 groups: those with rosiglitazone (rosiglitazone group, n = 49) and those without rosiglitazone (control group, n = 69). The rosiglitazone group was given rosiglitazone (4 mg/d) with previous treatment, insulin, or sulfonylurea, for 12 weeks, whereas the control group continued previous treatment with some dose modification for glycemic control. The patients had their blood glucose, lipid levels, as well as Lp(a) levels assessed to obtain a baseline, which were remeasured 12 weeks later. The fasting blood glucose and glycosylated hemoglobin (HbA(1c)) levels decreased significantly in both groups as compared with the baseline. The fasting glucose and HbA(1c) levels in both groups were similar at 12 weeks. The total cholesterol levels increased significantly in the rosiglitazone group (190.6 +/- 32.4 to 212.2 +/- 47.2 mg/dL, P =.002), while they were unchanged in the control group (185.4 +/- 36.8 to 188.0 +/- 35.8 mg/dL, P =.615). The triglyceride levels did not change in either group. Significant increases in high-density lipoprotein (HDL) cholesterol levels were observed in the rosiglitazone group as compared with the baseline (41.7 +/- 10.6 to 45.9 +/- 11.4 mg/dL, P =.004). The low-density lipoprotein (LDL) cholesterol levels increased significantly in the rosiglitazone group (120.5 +/- 29.9 to 136.3 +/- 40.0 mg/dL, P =.012), while they did not change in the control group (113.0 +/- 29.1 to 118.3 +/- 31.7 mg/dL, P =.234). Significant increases in Lp(a) levels were observed in the rosiglitazone group as compared with the baseline (22.4 +/- 17.4 to 25.7 +/- 20.5 mg/dL, P =.015), approximately a 15% increase in average values. In contrast, there was no change in Lp(a) levels in the control group. There was no correlation between the changes in Lp(a) and changes in fasting blood glucose or HbA(1c) levels in all study subjects. In summary, rosiglitazone increased serum total cholesterol, LDL cholesterol, as well as Lp(a) levels in patients with type 2 diabetes mellitus. Considering that patients with type 2 diabetes mellitus have increased risks for cardiovascular disease, caution should be taken when prescribing rosiglitazone to patients who already have other risk factors, such as hypertension and smoking.

Diabetes mellitus and coronary heart disease

Diabetes mellitus, especially type 2 diabetes, is a growing concern in America. Longitudinal trends show that obesity is more prevalent than in the past, and the incidence of type 2 diabetes is also increasing. Type 2 diabetes typically doubles the CHD risk in men and triples the risk in women. Intervening to control lipid levels and blood pressure has been shown to be especially helpful in preventing CHD, but the impact of better glycemic control on CHD risk is less convincing, especially in clinical trials. Revascularization studies in diabetics show that coronary bypass surgery is related to better outcomes than angioplasty procedures.

Differential influence of LDL cholesterol and triglycerides on lipoprotein(a) concentrations in diabetic patients

OBJECTIVE

To evaluate the relationship between plasma lipid profiles and lipoprotein(a) [Lp(a)] concentrations in diabetic patients, taking into account the Lp(a) phenotype.

RESEARCH DESIGN AND METHODS

We included 191 consecutive diabetic outpatients (69 type 1 and 122 type 2 diabetic patients) in a cross-sectional study Serum Lp(a) was determined by enzyme-linked immunosorbent assay, and Lp(a) phenotypes were assessed by SDS-PAGE followed by immunoblotting. The statistical methods included a stepwise multiple regression analysis using the Lp(a) serum concentration as the dependent variable. The lipid profile consisted of total cholesterol, HDL cholesterol, LDL cholesterol, corrected LDL cholesterol, triglycerides, and apolipoproteins AI and B.

RESULTS

In the multiple regression analysis, LDL cholesterol (positively) and triglycerides (negatively) were independently related to the Lp(a) concentration, and they explained the 6.6 and 7.8% of the Lp(a) variation, respectively. After correcting LDL cholesterol, the two variables explained 3.8 and 6.4% of the Lp(a) variation, respectively. In addition, we observed that serum Lp(a) concentrations were significantly lower in patients with type IV hyperlipidemia (mean 1.0 mg/dl [range 0.5-17], n = 16) than in normolipidemic patients (6.5 mg/dl [0.5-33.5], n = 117) and in type II hyperlipidemic patients (IIa 15.5 mg/dl [3.5-75], n = 13; IIb 9 mg/dl [1-80], n = 45); P < 0.001 by analysis of variance.

CONCLUSIONS

Lp(a) concentrations were directly correlated with LDL cholesterol and negatively correlated with triglyceride levels in diabetic patients. Therefore, our results suggest that the treatment of diabetic dyslipemia may indirectly affect Lp(a) concentrations.

Comparison of risk factors of macrovascular complications. Peripheral vascular disease, cerebral vascular disease, and coronary heart disease in Japanese type 2 diabetes mellitus patients

Although macroangiopathies such as peripheral vascular disease (PVD), cerebral vascular disease (CVD), and coronary heart disease (CHD) can often be observed in patients with diabetes mellitus, they are not specific for diabetes mellitus. Moreover, it is unclear whether their progressive mechanism is different. In the present study, we compared the risk factors among the diabetic macrovascular complications. Univariate analyses showed that in all patients, age at examination, duration of diabetes, thrombin-antithrombin III complex (TAT) level, fibrinogen level, lipoprotein (a) (Lp(a)) level, total cholesterol (T-Chol) level, and existence of microagiopathy were risk factors for PVD. Age, duration of diabetes, insulin level, TAT level, fibrinogen level, HDL cholesterol (HDL-Chol) level, hypertension, and nephropathy were risk factors for CVD. Only fibrinogen level was a risk factor for CHD. Moreover, Lp(a) level was a risk factor for PVD and CVD in male patients, but not in females. On the other hand, insulin level was a risk factor for CVD in female patients, but not in males. Multivariate analyses showed that TAT level, T-Chol level, and neuropathy were independent variables for PVD and that age, TAT level, and HDL-Chol level were independent variables for CVD. On the other hand, only fibrinogen level was the independent variable for CHD in males. Our results suggest that the progressive mechanism of PVD and CVD might be different from that of CHD and might differ according to gender in Japanese diabetic patients.

Effect of physical exercise on lipoprotein(a) and low-density lipoprotein modifications in type 1 and type 2 diabetic patients

To evaluate the effect of physical exercise on blood pressure, the lipid profile, lipoprotein(a) (Lp(a)), and low-density lipoprotein (LDL) modifications in untrained diabetics, 27 diabetic patients (14 type 1 and 13 type 2) under acceptable and stable glycemic control were studied before and after a supervised 3-month physical exercise program. Anthropometric parameters, insulin requirements, blood pressure, the lipid profile, Lp(a), LDL composition, size, and susceptibility to oxidation, and the proportion of electronegative LDL (LDL(-)) were measured. After 3 months of physical exercise, physical fitness improved (maximal O2 consumption [VO2max], 29.6 +/- 6.8 v 33.0 +/- 8.4 mL/kg/min, P < .01). The body mass index (BMI) did not change, but the waist circumference (83.2 +/- 11.8 to 81.4 +/- 11.2 cm, P < .05) decreased significantly. An increase in the subscapular to triceps skinfold ratio (0.91 +/- 0.37 v 1.12 +/- 0.47 cm, P < .01) and midarm muscle circumference ([MMC], 23.1 +/- 3.4 v 24.4 +/- 3.7 cm, P < .001) were observed after exercise. Insulin requirements (0.40 +/- 0.18 v 0.31 +/- 0.19 U/kg/d, P < .05) and diastolic blood pressure (80.2 +/- 10 v 73.8 +/- 5 mm Hg, P < .01) decreased in type 2 diabetic patients. High-density lipoprotein cholesterol (HDL-C) increased in type 1 patients (1.48 +/- 0.45 v1.66 +/- 0.6 mmol/L, P < .05), while LDL cholesterol (LDL-C) decreased in type 2 patients (3.6 +/- 1.0 v3.4 +/- 0.9 mmol/L, P < .01). Although Lp(a) levels did not vary in the whole group, a significant decrease was noted in patients with baseline Lp(a) above 300 mg/L (mean decrease, -13%). A relationship between baseline Lp(a) and the change in Lp(a) (r = -.718, P < .0001) was also observed. After the exercise program, 3 of 4 patients with LDL phenotype B changed to LDL phenotype A, and the proportion of LDL(-) tended to decrease (16.5% +/- 7.4% v 14.0% +/- 5.1%, P = .06). No changes were observed for LDL composition or susceptibility to oxidation. In addition to its known beneficial effects on the classic cardiovascular risk factors, regular physical exercise may reduce the risk of cardiovascular disease in diabetic patients by reducing Lp(a) levels in those with elevated Lp(a) and producing favorable qualitative LDL modifications.

The effect of long-term glycaemic control on serum lipoprotein(a) levels in patients with Type 2 diabetes mellitus

AIMS

To examine whether long-term glycaemic control affects lipoprotein(a) (Lp(a)) levels in patients with Type 2 diabetes mellitus.

METHODS

Eighty-nine Type 2 diabetic patients (38 men, 51 women) were recruited from the diabetes clinic. Based on HbA1c concentrations at baseline, patients were divided into two groups: those with HbA1c < 8.0% (n =45) and those with HbA1c > or = 8.0% (n=44). Comparisons of Lp(a) levels were made between both groups. The effect of long-term glycaemic control on Lp(a) levels was investigated in a subgroup of 20 patients, selected from those with baseline HbA1c > or = 8%. All these patients were treated with a goal of HbA1c <7%.

RESULTS

Lp(a) levels were not significantly different between those with HbA1c< 8.0% and those with HbA1c, > or = 8.0%. No correlation between Lp(a) and HbA1c or fasting blood glucose levels was noted in diabetic patients as a whole. After 2 years of intensive glycaemic control, all patients exhibited remarkable improvement of therapy: their average HbA1c levels were 6.5 +/- 0.7%, being < 7% in 70% of patients. However, no change in Lp(a) levels were observed after 2 years (19.5 +/- 14.8-21.4 +/- 13.4 mg/dl, P = 0.390).

CONCLUSION

These results indicate that improvement of glycaemic control does not affect serum Lp(a) levels in patients with Type 2 diabetes mellitus.

Hyperlipidemia and diabetes mellitus

The increased risk of coronary artery disease in subjects with diabetes mellitus can be partially explained by the lipoprotein abnormalities associated with diabetes mellitus. Hypertriglyceridemia and low levels of high-density lipoprotein are the most common lipid abnormalities. In type 1 diabetes mellitus, these abnormalities can usually be reversed with glycemic control. In contrast, in type 2 diabetes mellitus, although lipid values improve, abnormalities commonly persist even after optimal glycemic control has been achieved. Screening for dyslipidemia is recommended in subjects with diabetes mellitus. A goal of low-density lipoprotein cholesterol of less than 130 mg/dL and triglycerides lower than 200 mg/dL should be sought. Several secondary prevention trials, which included subjects with diabetes, have demonstrated the effectiveness of lowering low-density lipoprotein cholesterol in preventing death from coronary artery disease. The benefit of lowering triglycerides is less clear. Initial approaches to lowering the levels of lipids in subjects with diabetes mellitus should include glycemic control, diet, weight loss, and exercise. When goals are not met, the most common drugs used are hydroxymethylglutaryl coenzyme A reductase inhibitors or fibrates.

Correlation between serum lipoprotein(a) and angiographic coronary artery disease in non-insulin-dependent diabetes mellitus

OBJECTIVES

To examine the impact of diabetic state on the concentrations of lipoprotein(a) [Lp(a)] in patients with non-insulin-dependent diabetes mellitus (NIDDM) and the correlation between angiographic coronary artery disease (CAD) and serum Lp(a) concentrations in NIDDM.

DESIGN

In this cross-sectional study of 26 patients with NIDDM and 19 nondiabetic sex- and age-matched patients who underwent coronary angiography. CAD was assessed visually using coronary artery score (CAS), and plasma Lp(a) was measured by an enzyme-linked immunosorbent assay.

SETTING

The study was performed in an internal medicine clinic at a university hospital.

SUBJECTS

Twenty-six age- and sex-matched patients with NIDDM and 19 control patients without diabetes.

RESULTS

There was no significant difference between the Lp(a) concentrations of patients with NIDDM and nondiabetic subjects (P > 0.05). When patients with NIDDM were stratified by absence or presence of CAD, patients with CAD had higher levels of Lp(a) (P < 0.05). However, there was no significant correlation between the concentrations of Lp(a) and CAS (P > 0.05).

CONCLUSIONS

Diabetic state does not have any impact on Lp(a) concentrations. Lp(a) excess seems to be atherogenic in patients with NIDDM as shown in nondiabetic patients in previous studies. Although diabetic patients with CAD have higher Lp(a) concentrations than the diabetic patients without CAD, Lp(a) levels were not correlated with CAS.

Lipoprotein(a) concentration and molecular weight of apolipoprotein(a) in patients with cerebrovascular disease and diabetes mellitus

Plasma lipoprotein(a) [Lp(a)] concentrations are genetically determined, and hyper-Lp(a)-emia is an independent risk factor for atherosclerosis and thrombosis. To study the implications of Lp(a) in cerebrovascular disease (CVD) and diabetes mellitus (DM), we examined plasma Lp(a) levels and molecular weights of apolipoprotein(a) [apo(a)] in 118 patients with CVD, and 125 cases with DM. Although mean Lp(a) concentrations were higher in those cases with atherothrombotic brain infarction than in those with brain hemorrhage and lacunar infarction, the difference was not statistically significant. Lp(a) levels were significantly higher in the DM cases treated with insulin and in those treated with oral hypoglycemic agents than in those on diet therapy alone, suggesting that insulin and oral agents modulate apo(a) expression. Lp(a) concentrations correlated significantly with the low-molecular-weight isoforms of apo(a) in all CVD and DM groups.

Effects of visceral fat and weight loss on lipoprotein(a) concentration in subjects with obesity

We studied the relationships between regional body fat distribution and metabolic variables with lipoprotein(a) [Lp(a)] as well as the effects of weight loss on Lp(a) in 25 women and 9 men with obesity. Regional body fat distribution, as evaluated by the use of computed tomography; Lp(a); and fasting glucose, insulin, cholesterol, and triglycerides were analyzed before and after a very low-energy diet. No significant correlations were found between visceral, subcutaneous, and total fat and Lp(a) or between metabolic variables and Lp(a). All anthropometric variables significantly decreased after a very low-energy diet. Fasting glucose, insulin, triglycerides, and cholesterol significantly decreased after a very low-energy diet. No significant changes in Lp(a) concentration after a very low-energy diet were found. The correlation between the initial values of Lp(a) and changes of Lp(a) after a very low-energy diet was slightly significant (rho = 0.33, p < 0.06). In conclusion, our study shows that Lp(a) is not influenced by obesity, visceral fat, metabolic variables, or weight loss induced by a very low-energy diet.

Lipoprotein(a) concentrations and non-insulin-dependent diabetes mellitus: relationship to glycaemic control and diabetic complications

The aim of our study was to determine the lipoprotein(a) (Lp(a)) levels in patients with non-insulin-dependent diabetes mellitus (NIDDM) and to evaluate Lp(a) concentrations in relation to glycaemic control and diabetic complications. We evaluate in a cross-sectional study a total of 103 NIDDM patients (52 males and 51 females; mean age of 62.5 years; mean of diabetes duration: 12 years) referred to our hospital because of poor glycaemic control, and a group of 108 non-diabetic subjects (57 males and 51 females).

RESULTS

mean Lp(a) concentration did not significantly differ between NIDDM patients and non-diabetic subjects (11.1 +/- 14 vs. 16.2 +/- 14 mg/dl). The distribution of Lp(a) levels was highly skewed towards the lower levels in both groups, being over 30 mg/dl in only 6% of NIDDM patients and 12% of controls. Patients with Lp(a) levels over 10 mg/dl had lower haemoglobin Alc (HbA1c) than patients with Lp(a) levels over 10 mg/dl (8.5% vs. 10.4%; P < 0.01). Lp(a) concentration was positively correlated with body mass index (BMI) (P < 0.05) and HbA1c (P < 0.05). No association was found between Lp(a) and sex, age, other lipidic parameters, microalbuminuria, type of treatment and presence of cardiovascular disease. These findings may suggest that glycaemic control could have a modulatory role on Lp(a) concentration in NIDDM patients. In this study, diabetic complications did not seem to be associated with higher Lp(a) concentrations.

Lipoprotein (a) concentrations and apolipoprotein (a) phenotypes in normoglycaemic relatives of type 2 diabetic patients

Serum lipoprotein (a) concentrations (Lp(a)) are largely under genetic control, and are strong predictors of coronary heart disease. It has been hypothesised that Lp(a) may contribute to the increased risk of coronary heart disease in familial Type 2 diabetes mellitus. We therefore examined the Lp(a) concentrations and the apolipoprotein (a) (apo(a)) phenotypes in 126 normoglycaemic first degree relatives from families with two or more living Type 2 diabetic patients. These were compared with 147 sex matched normoglycaemic control subjects with no family history of diabetes. Lp(a) concentrations were measured using an enzyme-linked immunosorbent assay (ELISA), and apo(a) isoforms were determined and classified according to the relative mobility of apo(a) on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), relative to that of apolipoprotein B-100. There were no significant differences in Lp(a) concentrations between the relatives (R) and controls (C): 11.2 (R) vs. 11.1 (C) mg/dl (median). The distribution of apo(a) phenotypes was not significantly different between groups 0.65 (R) vs. 0.67 (C). These results show that first degree relatives at risk of developing Type 2 diabetes do not have abnormal Lp(a) concentrations or apo(a) phenotypes.

Serum lipoprotein-a levels and glyco-metabolic control in insulin and non-insulin dependent diabetes mellitus

OBJECTIVES

Conflicting results for lipoprotein-a (Lp(a)) levels in diabetic patients exist in the literature. Normal, increased, and decreased values are described, and a relation to glycometabolic control is not unequivocally established.

DESIGN AND METHODS

In our study Lp(a) was measured in a large group of diabetiee (80 patients with IDDM and 90 patients with NIDDM) in relation to glycometabolic control and the presence of microalbuminuria, retino and/or neuropathy. Long-term and short-term glycometabolic control were assessed by HbA1 and fructosamine assays, respectively.

RESULTS

Statistically significant differences between Lp(a) levels in IDDM and NIDDM-and a control group of 110 healthy nondiabetics could not be established. It appeared that the level of Lp(a) in IDDM and NIDDM is independent of short-term and long-term glycometabolic control or the occurrence of microalbuminuria, neuro or retinopathy. However, poor glycometabolic control affected the number of Lp(a) levels elevated above a threshold of 0.25 g/L in IDDM.

CONCLUSION

These results suggest that the level of Lp(a) in serum is not influenced by diabetes mellitus, glycemic control, or the occurrence of microalbuminuria, neuro or retinopathy.

Hypercoagulability and high lipoprotein(a) levels in patients with type II diabetes mellitus

Diabetes mellitus is associated with disturbances in hemostasis that could contribute to the development of diabetic vascular disease. We investigated the changes in parameters of blood coagulation and the fibrinolytic system and in plasma levels of lipoprotein(a)(Lp(a)) in 124 patients with type II diabetes mellitus and 44 healthy control subjects matched for age and body mass index (BMI) to determine whether hemostatic disturbances may lead to increased cardiovascular mortality. Median levels of fibrinogen (P < 0.0001), thrombin-antithrombin III complex (TAT) (P < 0.005), and plasminogen activator inhibitor-1 (PAI-1) activity (P < 0.05) in plasma were significantly elevated in diabetic patients compared with controls. The median concentration of Lp(a) was significantly higher in diabetic patients than in normal controls (18.2 vs. 12.6 mg/dl. P < 0.0005). Lp(a) levels tended to be elevated in patients with a prolonged history of diabetes. There was no evidence that Lp(a) levels were affected by metabolic control or by type of treatment. Twenty-two diabetics with coronary heart disease (CHD) had significantly higher levels of fibrinogen (P < 0.05), TAT (P < 0.05), and Lp(a) (24.7 vs. 13.7 mg/dl, P < 0.01) than the 51 patients without diabetic angiopathy. Our data indicate that impaired hemostatic balance in diabetes may cause hypercoagulability and may thus contribute to the increased cardiovascular mortality in diabetes.

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

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 (HbA1c 7.1 +/- 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) nondiabetic 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.

Lipoprotein(a) concentrations in non-insulin-dependent diabetes mellitus and borderline hyperglycemia: a population-based study

The objective of the study was to compare lipoprotein(a) [Lp(a)] concentrations in population-based samples of individuals with non-insulin-dependent diabetes mellitus (NIDDM), borderline hyperglycemia, and normoglycemia. From 2,740 male Italian Telephone Company employees aged 40 to 59 years participating in a health screening, we selected all those with NIDDM (n = 100) plus a random sample of 950 nondiabetic individuals. Diabetes was defined as fasting plasma glucose (FPG) of at least 140 mg/dL or current use of hypoglycemic drugs. Among nondiabetic individuals, 854 were defined as normoglycemic (FPG < 115 mg/dL) and 95 were defined as borderline hyperglycemic (115 < FPG < 140 mg/dL). Lp(a) level was measured on frozen plasma by enzyme-linked immunosorbent assay. Lp(a) concentrations were similar in people with NIDDM, borderline hyperglycemia, and normoglycemia: 11.2 +/- 14, 14.1 +/- 20, and 13.9 +/- 18 mg/dL, respectively (F = 1.03). Accordingly, the proportion of subjects with Lp(a) levels of at least 30 mg/dL was comparable in the three groups (12%, 15%, and 14%; chi 2 = 3.95, P = .41). Results were not confounded by differences in age, body mass index (BMI), waist to hip ratio, plasma lipids, alcohol consumption, physical activity, and use of drugs. Furthermore, within the diabetic group Lp(a) levels were not significantly different for those on diet only versus those on oral agents (10.8 +/- 14.1 v 11.7 +/- 14.7, P = .7) or for people with FPG of at least 180 as compared with people with FPG less than 180 mg/dL (9.9 +/- 12.8 v 11.5 +/- 14.8, P = .5).(ABSTRACT TRUNCATED AT 250 WORDS)

Longitudinal study of lipoprotein(a) in peripubertal children with insulin-dependent diabetes

We aimed to examine the longitudinal relationship between lipoprotein(a) and haemoglobin A1c, albumin excretion rate, and puberty in peripubertal children with insulin-dependent diabetes. A total of 114 patients aged 11.5 +/- 3.6 years (mean (SD)) were followed prospectively for 15.2 +/- 2.8 months. Lipoprotein(a), apolipoproteinB-100, haemoglobin A1c, mean overnight albumin excretion rate and Tanner stage were determined at the beginning and end of the study period. Lipoprotein(a) and apolipoproteinB-100 were measured using nephelometry. This method was correlated with radioimmunoassay and there was no significant change in mean bias during the study. Lipoprotein(a) fell significantly over time (214, (152, 276); 160 (84, 236) mg l-1 geometric mean (0.95 confidence intervals), p < 0.001); apolipoproteinB-100 did not change. Lipoprotein(a) and apolipoproteinB-100 did not differ in 233 cross-sectional controls of similar age. The change in lipoprotein(a) did not correlate with a small fall in haemoglobin A1c or with overnight albumin excretion rate, Tanner stage or insulin dose. Separate analysis of male and female patients and prepubertal and pubertal patients continued to show a significant fall in lipoprotein(a) independent of change in haemoglobin A1c or albumin excretion rate. Likewise, 53 patients with a change in haemoglobin A1c of greater than 1%, and 20 patients who progressed from normal albumin excretion rate to albumin excretion rate above the 95th centile, showed no relationship between lipoprotein(a) and haemoglobin A1c or albumin excretion rate. In conclusion, longitudinal changes in lipoprotein(a) do not relate to metabolic control or early changes in albuminuria in young patients with insulin-dependent diabetes.

The role of lipoprotein(a) in the vascular complications of diabetes mellitus

Lipoprotein(a) has been identified as an independent risk factor for atherosclerotic vascular disease in non-diabetic populations. Because of its potential role in the pathogenesis of both microvascular and macrovascular complications in diabetes, there have recently been many reports on lipoprotein(a) in diabetic populations. Some studies indicate an association between elevated lipoprotein(a) and macrovascular disease in non-insulin-dependent diabetes mellitus (NIDDM), but this link has not been found with insulin-dependent diabetes mellitus (IDDM). In IDDM, elevated lipoprotein(a) has been found in groups with diabetic nephropathy and retinopathy, raising the possibility that it plays a causative role. The relationship between glycaemic control and the lipoprotein(a) level has not been fully resolved. Most studies have not found any connection in NIDDM, but some found higher lipoprotein(a) levels in hyperglycaemic IDDM patients. Potentially, lipoprotein(a) is an important factor linking the microvascular and macrovascular complications of diabetes.

Effect of insulin treatment on serum lipoprotein(a) in non-insulin-dependent diabetes

In order to evaluate whether Lp(a), a lipoprotein that is potentially thrombogenic and atherogenic, is a potential risk factor for CAD in non-insulin-dependent diabetes (NIDDM), we compared the Lp(a) and its distribution in 145 NIDDM patients with that in 94 healthy control subjects. Furthermore, we studied the effect of insulin treatment on serum Lp(a) in 108 patients with NIDDM. Male and female NIDDM patients had similar Lp(a) concentrations to healthy controls (median value 167 mg L-1, range 15-1550 mg L-1 vs. 157 mg L-1, range 15-919 mg L-1, NS and 92, range 15-1190 mg L-1 vs. 103 mg L-1, range 15-842 mg L-1, NS). Also, the cumulative distribution of Lp(a) did not differ between the NIDDM patients and healthy subjects. Insulin treatment increased Lp(a) in diabetics with a Lp(a) concentration of less than 300 mg L-1, but this effect was not related to the concomitant improvement in metabolic control (mean change (+/- SEM) of HbA1c from 9.80 +/- 0.15 to 8.00 +/- 0.12; P < 0.001). In subjects with elevated Lp(a) concentrations (> 300 mg L-1) the Lp(a) concentration was unaffected by insulin, despite a similar improvement in glycaemic control. These results suggest that insulin may modulate the concentration of Lp(a).

A long-term, randomized, comparative study of insulin versus sulfonylurea therapy in type 2 diabetes

OBJECTIVES

To study the effect of insulin and sulfonylurea (SU) therapy on glycaemic control, insulin resistance and cardiovascular risk factors in type 2 diabetic subjects.

DESIGN

A prospective, parallel, randomized, controlled, long-term study.

SETTING

Outpatient clinic in tertiary referral centre.

SUBJECTS

Thirty-six type 2 diabetic subjects treated with diet and SU, aged 44-69 years and a duration of diabetes of between 2 and 14 years.

INTERVENTIONS

Individually adjusted doses of insulin and glibenclamide.

MAIN OUTCOME MEASURES

Glycosylated haemoglobin (HbA1c), insulin resistance (euglycaemic glucose clamp), levels of lipids, lipoproteins and blood pressure.

RESULTS

Glycaemic control improved during insulin treatment, but deteriorated on SU; HbA1c levels differed significantly between groups after 12 months of therapy (mean +/- SEM 7.9 +/- 0.3 vs. 9.5 +/- 0.4%, P = 0.004). Body mass index increased significantly during insulin treatment (26.4 +/- 0.7 to 27.8 +/- 0.7 kg/m2, P = 0.0001) and 30% of this increase was a result of an increase in lean body mass. The total glucose disposal rate showed a small increase in the insulin group. Levels of triglycerides and apolipoprotein B were significantly reduced during insulin treatment (1.8 +/- 0.2 to 1.5 +/- 0.2 mmol L-1, P = 0.03 and 1.58 +/- 0.1 to 1.40 +/- 0.08 g L-1, P = 0.003), and insulin prevented a reduction in the levels of high-density lipoprotein (HDL) cholesterol and apolipoprotein A-1 and an increase in Lp(a) lipoprotein observed in the SU group. Blood pressure levels did not change during therapy.

CONCLUSIONS

Insulin therapy was superior to SU treatment in achieving good metabolic control. Despite a modest improvement in cardiovascular risk factors in the insulin-treated group, no significant differences were observed between the groups after 1 year's treatment.

Decreased plasma levels of lipoprotein(a) in patients with hypertriglyceridemia

Lipoprotein(a) (Lp(a)) is an atherogenic lipoprotein which is similar in structure to, but metabolically distinct from, LDL. Factors modulating plasma Lp(a) concentrations are poorly understood. To investigate the possible interaction of Lp(a) with triglycerides, we determined the apo(a) phenotype, Lp(a) concentration, and distribution of Lp(a) in a group of patients with triglycerides > 400 mg/dl (n = 60) compared with a control group (n = 128). Lp(a) concentrations were significantly lower in hypertriglyceridemic patients (mean +/- S.E., 13 +/- 4 mg/dl; median, 6 mg/dl; 25/75 percentile, 2-13 mg/dl) as compared with the controls (mean, 22 +/- 2 mg/dl; median, 10 mg/dl; 25/75 percentile, 7-30 mg/dl). Plasma Lp(a) concentrations in the hypertriglyceridemic patients correlated negatively with triglyceride levels (r = -0.69, P = 0.03). The difference in Lp(a) levels between patients and controls was maintained when subjects were stratified by apo(a) phenotype and type of hyperlipidemia. After subdividing the hypertriglyceridemic patients into one group with apo(a) isoforms < or = S2 and one group with apo(a) isoforms > or = S3, we found that the differences in plasma Lp(a) concentrations between patients and controls were more pronounced in the group with the lower molecular weight apo(a) isoforms. These data indicate that hypertriglyceridemia is associated with lower plasma Lp(a) concentrations and suggest that increased levels of triglyceride-rich lipoproteins may influence the metabolism of Lp(a).

Structure and possible biological roles of Lp(a)

Lipoprotein(a) [Lp(a)] is a plasma macromolecular complex that is assembled from low-density lipoproteins (LDL) and a large hydrophilic glycoprotein, named apolipoprotein(a) [apo(a)], linked by a disulfide bond to apolipoprotein B-100. Apo(a) is formed by different structural domains one of which is present in multiple copies, the number of which is determined by variation in the hypervariable apo(a) gene. Sequence homology of apo(a) with plasminogen may explain the competition of Lp(a) for some physiological functions of plasminogen in the coagulation and fibrinolytic cascade in vitro. There is evidence that high plasma levels of Lp(a) may have atherogenic and/or thrombogenic potential. More work will have to be done to understand the exact role of Lp(a) in atherogenesis, to evaluate the potential synergy between Lp(a) and LDL in promoting coronary artery disease, and to assess the therapeutic benefits of a reduction of Lp(a) levels.

Lipids and Lp(a) lipoprotein levels and coronary artery disease in subjects with non-insulin-dependent diabetes mellitus

OBJECTIVE

To determine whether increased Lp(a) lipoprotein levels are associated with either non-insulin-dependent diabetes mellitus (NIDDM) or coronary artery disease (CAD) in patients with NIDDM and to examine the relationship between Lp(a) levels and glycemic control.

DESIGN

We conducted a cross-sectional study of subjects with NIDDM who were participants in the Rochester Diabetic Neuropathy Study and healthy control subjects from the population of Rochester, Minnesota.

MATERIAL AND METHODS

Lipids and Lp(a) lipoprotein levels were compared in 227 subjects with NIDDM and 163 control subjects and, among the subjects with NIDDM, in those with (N = 96) and without (N = 131) CAD. The correlation between Lp(a) levels and glycosylated hemoglobin was investigated.

RESULTS

Subjects with NIDDM had higher triglyceride and lower high-density lipoprotein cholesterol levels than did control subjects. Subjects with NIDDM and CAD had higher total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels and lower high-density lipoprotein cholesterol levels than did subjects with NIDDM without CAD. Subjects with NIDDM had significantly higher Lp(a) levels than did control subjects, but subjects with NIDDM and CAD did not have significantly higher Lp(a) levels than did those without CAD. Among subjects with NIDDM, the level of Lp(a) was not significantly correlated with glycosylated hemoglobin.

CONCLUSION

Although subjects with NIDDM have higher Lp(a) levels than do control subjects, Lp(a) does not seem to be associated with CAD in subjects with NIDDM. In this study, no association was found between Lp(a) level and glycemic control.

Lipoprotein disorders in diabetes mellitus

In IDDM or NIDDM, the total plasma cholesterol and triglycerides are usually within normal limits when the blood glucose is controlled. Marked hypertriglyceridemia can develop with loss of glycemic control and is often due to superimposed genetic abnormalities in lipoprotein metabolism. Tight control in IDDM usually reduces LDL and VLDL to normal levels and may raise HDL above the normal range. Low HDL cholesterol and mild to moderate elevations of VLDL triglyceride are common in NIDDM if obesity or proteinuria is also present. Both HDL and LDL may be smaller and more dense and may be enriched with triglyceride as compared with cholesterol. These abnormalities may require weight loss for control. The increased incidence of cardiovascular disease in diabetes is unexplained but is amplified by the well-defined cardiovascular risk factors. The new American Diabetes Association guidelines call for treatment of high triglycerides and LDL cholesterol to be aggressively reduced. Triglycerides should be under 200 mg/dL, are considered borderline high between 200 and 400 mg/dL, and high when above 400 mg/dL. Low HDL is defined as less than 35 mg/dL. Control of obesity with diet and exercise and reduced intake of saturated fat and cholesterol are important first steps. If needed, drug therapy is appropriate to reduce LDL to levels below 130 mg/dL in all adult diabetics and below 100 mg/dL in those with cardiovascular disease.

Apolipoprotein(a) phenotypes and serum lipoprotein(a) levels in maintenance hemodialysis patients with/without diabetes mellitus

We studied the quantitative and qualitative characteristics of lipoprotein(a) [Lp(a)] as a function of apolipoprotein(a) [apo(a)] phenotypes in 152 patients (123 males, 29 females) undergoing maintenance hemodialysis (HD) with or without diabetes mellitus (DM), in 101 patients with diabetes mellitus without hemodialysis (58 males, 43 females), and in 421 normal controls (333 males, 88 females). Serum Lp(a) levels were significantly (P < 0.01) higher in patients than in controls (26.2 +/- 18.3 mg/dl in HD with DM, 26.4 +/- 22.0 mg/dl in HD without DM, 27.1 +/- 27.3 mg/dl in DM without HD, and 14.9 +/- 13.7 mg/dl in controls, respectively). Apo(a) phenotyping was performed by a sensitive, high resolution technique using SDS-agarose/gradient (3 to 6%) PAGE. In normal controls, the molecular weights of apo(a) isoforms were inversely correlated with plasma Lp(a) levels, and the same tendency was found in patients who were undergoing hemodialysis and/or who had diabetes mellitus. We assumed the differences in apo(a) phenotypes detectable with our method reflected consecutive differences in molecular weights of apo(a). The results of an analysis of covariance and a least square means comparison indicated that the regression lines between serum Lp(a) levels [log Lp(a)] and apo(a) phenotypes in patient groups were significantly (P < 0.01) elevated for every apo(a) phenotype, as compared to the regression line of the control group. Even after the low molecular weight apo(a) phenotypes (A1-A8) were omitted, the same tendency was observed. However, no differences were observed between the patient groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Alteration of lipoprotein(a) concentration with glycemic control in non-insulin-dependent diabetic subjects without diabetic complications

Recently, a high plasma level of lipoprotein(a) [LP(a)] has been considered an independent risk factor for atherosclerosis and its sequelae, particularly myocardial infarction. Patients with non-insulin-dependent diabetes mellitus (NIDDM) have an increased mortality rate from cardiovascular and cerebrovascular disease. Therefore, plasma concentrations of Lp(a) were determined and the relationship between fasting plasma Lp(a) level and diabetic control was investigated in NIDDM patients without any diabetic complications. Fasting plasma Lp(a) levels were measured using enzyme-linked immunosorbent assay kits [Terumo Medical Corp, Elkton, MD, Lp(a)] in 61 NIDDM subjects (30 men aged 56 +/- 2.0 years, 31 women aged 53 +/- 2.1 years [mean +/- SEM]) who were without any diabetic macroangiopathy and microangiopathy such as retinopathy, nephropathy, and neuropathy and in 56 healthy age- and sex-matched controls. Plasma Lp(a) levels were significantly higher in the diabetic group than in the control group (23.5 +/- 2.5 v 11.7 +/- 1.4 mg/dL [mean +/- SEM], P < .001). There was no significant correlation between log-transformed plasma Lp(a) levels and other factors such as age, sex, body mass index (BMI), blood pressure, duration of diabetes, fasting plasma glucose (FPG) level, glycosylated hemoglobin (HbA1C) level, and plasma lipid levels except for low-density lipoprotein cholesterol (LDL-C) levels in diabetic patients. A significant positive correlation was noted in diabetic patients between the changes of log Lp(a) and HbA1C levels after a 3-month follow-up period (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of progressively increasing albuminuria to apoprotein(a) and blood pressure in type 2 (non-insulin-dependent) and type 1 (insulin-dependent) diabetic patients

This study has explored the temporal relationship between apoprotein(a), blood pressure and albuminuria over a mean interval of 11 years in a cohort of 107 diabetic patients of whom 26 (14 Type 2 (non-insulin-dependent), 12 Type 1 (insulin-dependent) had progressively increasing albuminuria ('progressors'). In Type 2 diabetic patients, no significant differences were noted for HbA1, blood pressure, creatinine clearance or serum lipids between progressors and non-progressors. In Type 1 diabetic patients, final systolic and diastolic blood pressures were higher in progressors compared with non-progressors and progressors showed impairment of renal function in association with a rise in blood pressure at the macroalbuminuric stage. Initial apoprotein(a) levels were similar in progressors and non-progressors of either diabetes type. Apoprotein(a) levels increased exponentially with time in 12 of 14 Type 2 progressors but only in 5 of 12 Type 1 progressors (p < 0.01). In Type 2 diabetic patients, the annual increase in apoprotein(a) levels was 9.1 +/- 2.4%, which was significantly greater than in non-progressors, 2.0 +/- 1.2% (p < 0.01) and also exceeded the rates of increase of apoprotein(a) in progressors with Type 1 diabetes, 4.0 +/- 1.4%, (p < 0.05). Apoprotein(a) levels correlated significantly with albuminuria in 8 of 14 Type 2 progressors but only in 3 of 12 Type 1 progressors (p < 0.05). The rate of increase of apoprotein(a) levels was not related to mean HbA1, creatinine or creatinine clearance levels, or to albuminuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoprotein(a) levels in relation to diabetic complications in patients with non-insulin-dependent diabetes

The relationship between serum levels of lipoprotein(a) Lp(a)) and the presence of chronic diabetic complications was studied in 194 patients with non-insulin-dependent diabetes mellitus (NIDDM; 75 males, 119 females; age 66 +/- 11 years; duration of diabetes, 11 (range 1-35) years). They were taking various treatments (diet alone, oral hypoglycaemic agents and/or insulin). Metabolic status and prevalence of diabetic complications were assessed by detailed history, physical examination, laboratory analysis and ECG. Average metabolic control was moderate (HbA1c 8.2 +/- 1.7%). Median serum Lp(a) level was 183 U l-1 (range 8-2600 U l-1), which was significantly higher than in control subjects of comparable age (median 101; range 8-1747 U l-1; P < 0.05), while HDL-cholesterol levels were lower (1.14 +/- 0.38 vs. 1.35 +/- 0.35 mmol l-1; P = 0.001), and total cholesterol levels were comparable. No significant relationships between diabetes treatment or metabolic control and Lp(a) levels were observed. In the quartile of patients with the highest Lp(a) levels, total cholesterol and triglycerides were slightly higher (P < 0.05), whereas HDL-cholesterol was not different. With increasing Lp(a) levels, higher prevalences of preproliferative retinopathy and of coronary artery disease (CAD) were observed, but not of the other complications. No relationship was found between the degree of albuminuria and Lp(a) levels. We conclude that in NIDDM patients, Lp(a) levels are elevated compared with non-diabetic subjects, and that higher Lp(a) levels are associated with higher prevalences of CAD and of retinopathy.

High serum lipoprotein(a) levels are an independent risk factor for cerebral infarction

BACKGROUND AND PURPOSE

This study was conducted to evaluate the role of high serum lipoprotein(a) levels in a group of patients with a relatively early onset of cerebral infarction as a whole and in a subgroup with the perforating artery occlusion subtype of cerebral infarction.

METHODS

Fifty-four patients with cerebral infarction, the onset of which was before age 65 years (37 men, 17 women; mean age, 61.9 +/- 7.7 years) were examined in this study. When patients with atrial fibrillation were excluded to omit cardiac embolic strokes from analysis, the group consisted of 45 patients. The patients were classified into two subtype groups, the perforating artery occlusion group and the cortical artery occlusion group, by using magnetic resonance imaging. Lipoprotein(a) levels were measured by an enzyme-linked immunosorbent assay. Four biochemical variables (serum levels of lipoprotein(a), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides) and other potential risk factors such as hypertension, diabetes mellitus, smoking habits, alcohol intake, and family history were analyzed by stepwise logistic regression to determine the independent and significant risk factors for cerebral infarction without atrial fibrillation.

RESULTS

The incidence of subjects with serum lipoprotein(a) levels > or = 42.6 mg/dL, which is the 95th percentile level of the control subjects, was significantly increased in the total cerebral infarction group (P < .025) and the perforating artery occlusion group (P < .025) compared with the control group. In addition, by using stepwise logistic regression analysis in the total and perforating artery occlusion patient groups we identified three independent and significant risk factors: hypertension, a low high-density lipoprotein cholesterol level, and a high serum lipoprotein(a) level. In the cortical artery occlusion group, the sample size was not large enough for the statistical analysis. Diabetes mellitus is the only known factor that correlates with serum lipoprotein(a) levels, but there were no significant correlations between serum lipoprotein(a) levels and history of diabetes mellitus or fasting blood sugar.

CONCLUSIONS

These findings indicate that high serum lipoprotein(a) levels are an independent risk factor in the development of cerebral infarction when subjects with atrial fibrillation were excluded from the total group and the perforating artery occlusion subtype group.

Improved blood glucose control by insulin therapy in type 2 diabetic patients has no effect on lipoprotein(a) levels

The effects of improved blood glucose control by insulin therapy on lipoprotein(a) and other lipoproteins were studied in 54 patients with Type 2 diabetes (mean +/- SD: age 67 +/- 9 years, body mass index 26.1 +/- 4.4 kg m-2, median duration of diabetes 10 (range 1-37) years, 23 males, 31 females), who were poorly controlled despite diet and maximal doses of oral hypoglycaemic agents. After 6 months of insulin treatment, mean fasting blood glucose concentrations had decreased from 14.1 +/- 2.2 mmol l-1 to 8.4 +/- 1.8 mmol l-1 (p < 0.001), and HbA1c had fallen from 11.1 +/- 1.4% to 8.2 +/- 1.1% (p < 0.001). Significant decreases of total and LDL cholesterol, triglycerides, apolipoprotein B, and free fatty acids were observed, while HDL-cholesterol and apoA1 increased by 10%. Baseline serum Lp(a) levels were elevated compared to non-diabetic subjects of similar age (median 283, range 8-3050 mg l-1, vs 101, range 8-1747 mg l-1, p < 0.05), but did not change with insulin, and there was no correlation with the degree of metabolic improvement and changes in Lp(a) levels. It is concluded that improved blood glucose control by insulin therapy does not alter elevated Lp(a) levels in Type 2 diabetic patients, but has favourable effects on the other lipoproteins.

Apolipoprotein E phenotype is related to macro- and microangiopathy in patients with non-insulin-dependent diabetes mellitus

The role of apoliprotein E (apo E) in modulating the susceptibility of individuals with non-insulin-dependent diabetes mellitus (NIDDM) to atherosclerotic vascular disease was studied in 143 male and 128 female patients with NIDDM. The data show that the apolipoprotein phenotype E2 somehow protects from macrovascular complications in NIDDM both in men and women. E2 also tends to protect from microvascular complications. In contrast, apo E phenotypes E4/4 and E4/3 tend to increase the risk for macroangiopathy in NIDDM patients. The lower prevalence of macroangiopathy in the subjects with E2 was associated with lower plasma total and LDL cholesterol concentrations and low plasma lipoprotein(a) levels. Overall, this study demonstrates the role of the apo E phenotype to modulate the risk for diabetic complications in patients with NIDDM. The confirmation of the association of apo E polymorphism with diabetic complications warrants, however, long-term follow-up studies.

Improvement of lipid profile in type 2 (non-insulin-dependent) diabetes mellitus by insulin-like growth factor I

Type 2 (non-insulin-dependent) diabetes mellitus is associated with increased glucose, insulin, total and VLDL-triglyceride, and often total and LDL-cholesterol levels which promote vascular disease. Recombinant human insulin-like growth factor-I which mimics many effects of insulin, decreased insulin, total and VLDL-triglyceride, and total and LDL-cholesterol levels in healthy man as well as glucose and insulin levels in Type 2 diabetic patients. We, therefore, investigated total and fractionated triglyceride and cholesterol levels, lipoprotein(a), non-esterified fatty acid, and apolipoprotein levels in eight Type 2 diabetic patients during five control, five treatment, and three wash-out days. They received a constant diet throughout and daily 2 x 120 micrograms insulin-like growth factor-I/kg s.c. during the treatment period. Fasting total and VLDL-triglyceride, total and LDL-cholesterol control levels were (mean +/- SD) 3.1 +/- 2.6, 1.3 +/- 1.0, 6.3 +/- 1.3, and 4.5 +/- 1.1 mmol/l and decreased to 1.6 +/- 0.8, 0.6 +/- 0.4, 5.0 +/- 1.0, and 3.5 +/- 1.1 mmol/l, respectively, on the last treatment day (p < 0.01). During therapy, fasting lipoprotein(a) levels and the postprandial area under the triglyceride curve decreased by 48 +/- 22 and 32 +/- 18% of control (p < 0.01), respectively. In conclusion, insulin-like growth factor-I lowered lipid levels in Type 2 diabetic patients directly or indirectly or both because of decreased glucose and insulin levels. Long-term trials would be of interest with respect to the cardiovascular risk in Type 2 diabetes and patients with hyperlipidaemia.

Cardiovascular risk factors in non-insulin-dependent diabetic subjects with microalbuminuria

In subjects with insulin-dependent diabetes mellitus, microalbuminuria has been associated with increased triglyceride and lipoprotein (a) (Lp[a]) concentrations and increased blood pressure. However, few studies have examined whether this association is present in subjects with non-insulin-dependent diabetes mellitus (NIDDM). We measured lipids, lipoproteins, Lp(a), blood pressure, and albumin excretion in 234 subjects with NIDDM from the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Seventy-two subjects had microalbuminuria (> or = 30 mg/dl). These subjects had increased systolic and diastolic blood pressures and higher fasting glucose concentrations relative to subjects without microalbuminuria. However, there were no significant differences between subjects with and without microalbuminuria with respect to lipids, lipoproteins, Lp(a), self-reported myocardial infarction, obesity, or body fat distribution. Subjects with diabetic retinopathy had increased microalbuminuria. In multivariate analysis both glycemia and blood pressure continued to be significantly related to the presence of microalbuminuria. We conclude that NIDDM subjects with microalbuminuria have elevated blood pressure and more severe glycemia but do not have a significantly more atherogenic pattern of lipids, lipoproteins, or Lp(a) than subjects without microalbuminuria.

Plasma lipoprotein (a) concentration and phenotypes in diabetes mellitus

Patients with Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetes mellitus are at increased risk of developing atherosclerotic vascular diseases. A variety of lipoprotein abnormalities have been described as being associated with this increased risk. In this study, apo(a) isoform frequencies and lipoprotein(a) [Lp(a)] concentrations were determined in Type 1 and Type 2 diabetic patients in order to investigate a possible contribution of Lp(a) to the increased risk for atherosclerosis in diabetes. No significant differences in plasma Lp(a) concentrations were found in two ethnically different populations (Austrians from the province of Tyrol and Hungarians from Budapest) in either type of diabetes when compared to respective control groups (91 Type 1 and 112 Type 2 diabetic patients vs 202 control subjects in the Hungarian study and 44 Type 1 diabetic and 44 Type 2 diabetic vs 125 control subjects in the Austrian study). There were also no significant apo(a) isoform frequency differences between both patient groups and control subjects in the two study groups. These data, obtained from two large ethnically different populations, provide no evidence of a contribution of Lp(a) to the increased risk for atherosclerosis in diabetes.

Plasma apolipoprotein (a) is increased in type 2 (non-insulin-dependent) diabetic patients with microalbuminuria

Patients with Type 2 (non-insulin-dependent) diabetes mellitus complicated by microalbuminuria or albuminuria, have an increased risk of developing macrovascular disease and of early mortality. Because lipoprotein abnormalities have been associated with diabetic nephropathy, this study tested the hypothesis that levels of apolipoprotein (a) are elevated in patients with Type 2 diabetes and increased levels of urinary albumin loss. Levels of apolipoprotein (a) in diabetic patients with microalbuminuria (n = 26, geometric mean 195 U/l, 95% confidence interval 117-324) and albuminuria (n = 19, 281 U/l, 165-479) were higher than in non-diabetic control subjects (n = 140, 107 U/l, 85-134, p < 0.05), and in the albuminuric group than diabetic patients without urinary albumin loss (n = 58, 114 U/l, 76-169, p < 0.05). Patients with microalbuminuria and albuminuria had levels comparable with patients undergoing elective coronary artery graft surgery (n = 40, 193 U/l, 126-298). Apolipoprotein (a) levels were higher in diabetic patients with macrovascular disease than in those without (n = 49, 209 U/l, 143-306 vs n = 54, 116 U/l, 78-173, p < 0.05). These preliminary results suggest that raised apolipoprotein (a) levels of Type 2 diabetic patients with microalbuminuria and albuminuria may contribute to their propensity to macrovascular disease and early mortality.