Association of lipoprotein(a) levels and apolipoprotein(a) phenotypes with coronary artery disease in Type 2 diabetic patients and in non-diabetic subjects

South Asian Cardiovascular Disease & Cancer Risk: Genetics & Pathophysiology

South Asians (SAs) are at heightened risk for cardiovascular disease as compared to other ethnic groups, facing premature and more severe coronary artery disease, and decreased insulin sensitivity. This disease burden can only be partially explained by conventional risk factors, suggesting the need for a specific cardiovascular risk profile for SAs. Current research, as explored through a comprehensive literature review, suggests the existence of population specific genetic risk factors such as lipoprotein(a), as well as population specific gene modulating factors. This review catalogues the available research on cardiovascular disease and genetics, anthropometry, and pathophysiology, and cancer genetics among SAs, with a geographical focus on the U.S. A tailored risk profile will hinge upon population customized classification and treatment guidelines, informed by continued research.

Lipoprotein (a) as a cause of cardiovascular disease: insights from epidemiology, genetics, and biology

Human epidemiologic and genetic evidence using the Mendelian randomization approach in large-scale studies now strongly supports that elevated lipoprotein (a) [Lp(a)] is a causal risk factor for cardiovascular disease, that is, for myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis. The Mendelian randomization approach used to infer causality is generally not affected by confounding and reverse causation, the major problems of observational epidemiology. This approach is particularly valuable to study causality of Lp(a), as single genetic variants exist that explain 27-28% of all variation in plasma Lp(a). The most important genetic variant likely is the kringle IV type 2 (KIV-2) copy number variant, as the apo(a) product of this variant influences fibrinolysis and thereby thrombosis, as opposed to the Lp(a) particle per se. We speculate that the physiological role of KIV-2 in Lp(a) could be through wound healing during childbirth, infections, and injury, a role that, in addition, could lead to more blood clots promoting stenosis of arteries and the aortic valve, and myocardial infarction. Randomized placebo-controlled trials of Lp(a) reduction in individuals with very high concentrations to reduce cardiovascular disease are awaited. Recent genetic evidence documents elevated Lp(a) as a cause of myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis.

Lipoprotein (a) and atherogenic indices in Sudanese patients with type 2 diabetes

BACKGROUND & AIMS

Type 2 diabetes is associated with significant cardiac morbidity and mortality with a more than threefold increased risk of coronary artery disease (CAD). We aimed to assess the serum concentrations of lipoprotein (a) and lipid profile indexes as predictors for CAD in Sudanese type 2 diabetics compared to healthy subjects.

MATERIALS & METHODS

This case-control study was conducted at Jabir Abu-Aliz Specialized Center, Khartoum State, Sudan. After overnight fasting, 4 ml blood samples were collected in plain vials through venous puncture from each subject. Lipid profile parameters were estimated by standard laboratory procedures. Serum lipoprotein (a) was measured by immunoturbidimetric method. Statistical analyses were performed using SPSS software (version 17).

RESULTS

Compared to healthy controls, type 2 diabetics showed significantly higher serum lipids and lipoprotein fractions. The mean values of lipoprotein (a), TC: HDL-C (5.55±.8 vs. 3.89±.6) and LDL-C: HDL-C (3.80±0.7 vs. 2.32±0.5) were significantly increased in patients. Lipoprotein (a) was significantly correlated with TG (p=.025), HDL-C (inversely, p<.001), VLDL-C (p= .025), and TC: HDL-C ratio (p= 016). Moreover, LDL-C: HDL-C ratio and TC were the most common risk factors distributed among the study patients (80% and 71.4% respectively).

CONCLUSION

Diabetic patients characterized by higher ratios of TC: HDL -C and LDL: HDL and Lipoprotein (a) compared to healthy controls. The evaluation of these lipid indices in diabetics, beside the routine lipid profile analysis, may be a crucial helpful step in the prevention of coronary artery disease since these atherogenic factors can be reduced by lifestyle modifications.

Lipoprotein(a) and cardiovascular disease in diabetic patients

Lipoprotein(a) (Lp[a]) is a LDL-like particle consisting of an ApoA moiety linked to one molecule of ApoB(100). Recent data from large-scale prospective studies and genetic association studies provide highly suggestive evidence for a potentially causal role of Lp(a) in affecting risk of cardiovascular disease (CVD) in general populations. Patients with Type 2 diabetes display clustered metabolic abnormalities and elevated risk of CVD. Lower plasma Lp(a) levels were observed in diabetic patients in several recent studies. Epidemiology studies of Lp(a) and CVD risk in diabetic patients generated inconsistent results. We recently found that Lp(a)-related genetic markers did not predict CVD in two diabetic cohorts. The current data suggest that Lp(a) may differentially affect cardiovascular risk in diabetic patients and in the general population. More prospective studies, Mendelian randomization analysis and functional studies are needed to clarify the causal relationship of Lp(a) and CVD in diabetic patients.

Lipoprotein(a) and homocysteine as genetic risk factors for vascular and neuropathic diabetic foot in type 2 diabetes mellitus

Neuropathy and peripheral artery disease represent the main pathophysiological conditions underlying diabetic foot. Several studies showed that Lipoprotein(a)-Lp(a)-and homocysteine (Hcy) can be associated with diabetic complications, but their relationship with diabetic foot is unclear. Aim of this study was to investigate whether Lp(a) and Hcy were associated with diabetic foot ulcerations, classified according to the presence of peripheral artery disease (PAD) or neuropathy. From among consecutive type 2 diabetic attending at the Diabetic Foot Clinic 27 subjects with vascular diabetic foot (VDF), 43 with neuropathic diabetic foot (NDF) and 52 controls without foot ulceration, neuropathy, and PAD were enrolled. Both Lp(a) (26.1 ± 22.7 vs. 14.9 ± 19.5 mg/dl; P = 0.003) and Hcy levels (15.4 ± 5.7 vs. 12.2 ± 5.1 μmol/l; P = 0.022) were significantly greater in the VDF group than in controls. Lp(a) levels were significantly lower in the NDF group than in controls (6.9 ± 8.1 versus 14.9 ± 19.5 mg/dl; P = 0.009), while no difference in Hcy levels was found. Multiple logistic regression analysis showed that Hcy was associated with VDF (OR: 1.11; 95% CI: 1.07-14.1; P = 0.048). Lp(a) did not enter the model, but its P-value was very near to the significant level (OR: 1.09; 95% CI: 0.99-12.05; P = 0.059). Moreover, low Lp(a) levels were associated with NDF (OR: 0.84; 95% CI: 0.21-0.96; P = 0.039). Our study has shown for the first time that high Lp(a) and Hcy levels are associated with the development of VDF, while low Lp(a) levels appear to be associated with delayed wound healing in patients with neuropathic foot ulcerations.

Lipoprotein a: where are we now?

PURPOSE OF REVIEW

To provide an update of the literature describing the link between lipoprotein a and vascular disease.

RECENT FINDINGS

There is evidence that elevated plasma lipoprotein a levels are associated with coronary heart disease, stroke and other manifestations of atherosclerosis. Several mechanisms may be implicated, including proinflammatory actions and impaired fibrinolysis.

SUMMARY

Lipoprotein a potentially represents a useful tool for risk stratification in the primary and secondary prevention setting. However, there are still unresolved methodological issues regarding the measurement of lipoprotein a levels. Targeting lipoprotein a in order to reduce vascular risk is hampered by the lack of well tolerated and effective pharmacological interventions. Moreover, it has not yet been established whether such a reduction will result in fewer vascular events. The risk attributed to lipoprotein a may be reduced by aggressively tackling other vascular risk factors, such as low-density lipoprotein cholesterol.

Interactions of lipoprotein(a) with diabetes mellitus, apolipoprotein B and cholesterol enhance the prognostic values for coronary artery disease

BACKGROUND

Synergistic interactions between elevated serum lipoprotein(a) [Lp(a)] and other unfavorable risk factors have been proposed to cause very high risk for coronary artery disease (CAD). The aim of this study was to examine the potential interactions between Lp(a) and other risk factors.

METHODS

The profiles of serum (apo)(lipo)proteins, markers of inflammation, indicators of hemoconcentration as well as classical risk factors were determined in 264 clinically stable angiographically documented subjects. Correlation, linear and logistic regression and stratification analyses were performed.

RESULTS

The frequency and severity of CAD and the prevalence of diabetes mellitus were significantly higher in the 3rd relative to 1st tertile of Lp(a). Subjects with Lp(a) levels in the upper tertile had significantly higher levels of serum glucose, total cholesterol and low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (apoB), calcium, phosphate and their ion product. Bivariate correlation analysis indicated that serum Lp(a) was associated positively with the occurrence and severity of CAD, diabetes mellitus and the levels of serum glucose, cholesterol, LDL-C, apoB, calcium, phosphate and inversely to physical inactivity. In linear regression analysis, LDL-C (or apoB), diabetes, physical inactivity and phosphate were the major independent determinants of Lp(a) values. In multiple logistic regression analysis, after adjusting for major risk factors, Lp(a) showed a significant and independent association with the prevalence of CAD. By constructing dummy combined variables, elevated Lp(a) accompanied with diabetes or high levels of serum glucose, apoB and cholesterol exhibited an amplified high risk for CAD.

CONCLUSIONS

The results indicate that serum Lp(a) does interact multiplicatively with diabetes, apoB and cholesterol. The simultaneous assessment of Lp(a) and interactive risk factors enhances the discriminating value for CAD.

Lipoprotein(a): an independent risk factor for ischemic heart disease that is dependent on triglycerides in subjects with type 2 diabetes mellitus

Lipoprotein(a) is an independent risk factor for Ischaemic Heart Disease (IHD) in the general population. There are conflicting reports in the extent of its association with IHD among subjects with Type 2 diabetes mellitus (T2DM).

The aim was to determine the concentration of Lp(a) and its relationship with other lipids parameters among Omani T2DM subjects with and without IHD. An over-night fasting blood sample from 221 T2DM subjects (86 females and 135 males) and 156 non-diabetics (69 females and 87 males) aged 30–70 years (as control) was taken for lipid profile studies.

Lp(a) was significantly lower (p = 0.012) among T2DM subjects 0.123(1.12) g/L compared to non-diabetics 0.246 (1.18)g/L, irrespective of gender.

A significant correlation (Spearman correlation, P = 0.047) was revealed between Lp(a) and IHD among Omani T2DM subjects. The proportions of T2DM subjects with IHD and an Lp(a) >0.3 g/L was higher compared to T2DM without IHD irrespective of gender, for women 42% vs. 27% and for men 17.5 vs. 8%, respectively.

A significant negative correlation existed between Lp(a) and triglycerides (r = 0.41, P = 0.002) among T2DM subjects. In contrast, a significant positive correlation existed between Lp(a) and LDL-chol among the non-diabetic subjects.

Women had significantly higher Lp(a) concentration compared to men ( 0.30 Vs. 0.16 g/L, P < 0.0001) irrespective of the diabetic status.

Lp(a) is an independent risk factor for IHD among Omani T2DM subjects. Lp(a) concentration was significantly lower and negatively correlated with triglycerides among Omani diabetic compared to non-diabetic subjects.

Lipoprotein(a), type 2 diabetes and vascular risk in coronary patients

BACKGROUND

Lipoprotein(a) [Lp(a)] is an important cardiovascular risk factor in the general population. However, prospective data on the vascular risk conferred by Lp(a) in patients with diabetes mellitus are scarce and controversial. It is not known whether the diabetic state affects the association of Lp(a) with vascular events among coronary patients.

DESIGN

We measured Lp(a) in 587 consecutive patients undergoing coronary angiography for the evaluation of coronary artery disease. The incidence of vascular events was recorded over 4 years.

RESULTS

At baseline, Lp(a) was significantly lower in patients with type 2 diabetes (T2DM) (n = 136) than in nondiabetic individuals (11 (0.8-30) mg dL(-1) vs. 16 (0.8-51) mg dL(-1); P = 0.025). Prospectively, Lp(a) was a strong and independent predictor of vascular events in nondiabetic patients (standardized adjusted hazard ratio (HR) = 1.461 (1.121-1.904); P = 0.005), but not in patients with T2DM [HR = 0.812 (0.539-1.223); P = 0.320]. An interaction term diabetes x Lp(a) was significant (P = 0.008), indicating that Lp(a) was a significantly stronger predictor of vascular events in nondiabetic patients than in patients with T2DM.

CONCLUSIONS

Lp(a) in diabetic coronary patients is low and not associated with the incidence of vascular events. Although measurement of Lp(a) provides useful information in nondiabetic coronary patients, it is of little value in coronary patients with T2DM.

Predictors of coronary artery disease in the Lebanese population

BACKGROUND

Coronary artery disease (CAD) is one of the major causes of morbidity and mortality in the world. The disease is determined by many risk factors such as age, gender, diabetes, dyslipidemia, smoking, as well as elevated serum levels of lipoprotein (a) (Lp(a)), homocysteine, C-reactive protein (CRP) and uric acid. In this study, we evaluated the association of biologic and metabolic parameters with CAD in a group of Lebanese patients.

METHODS

Three hundred patients were recruited for the study. Biologic and blood metabolic parameters were measured. Patients were then divided into 3 groups according to their catheterization result: 0% stenosis (controls), <50% stenosis and >or=50% stenosis.

RESULTS

Hyperlipidemias, CRP, homocysteine and uric acid levels in CAD patients were not different from those of the controls. However, age, elevated fasting blood glucose (FBG) and elevated serum Lp(a) levels were found to be strong independent predictors of CAD in our study population. Association with CAD was also shown for gender, hypertension, diabetes and family history of CAD.

CONCLUSION

We report the importance of serum Lp(a) levels and FBG in the prediction and prevention of CAD in our population.

Prospective study of lipoprotein(a) as a risk factor for deteriorating renal function in type 2 diabetic patients with overt proteinuria

OBJECTIVE

The effect of lipoprotein(a) [Lp(a)] on the progression of diabetic nephropathy has not been evaluated yet. The aim of this study was to determine whether Lp(a) is an independent risk factor for deteriorating renal function in type 2 diabetic patients with nephropathy.

RESEARCH DESIGN AND METHODS

We conducted this prospective study in type 2 diabetic patients with overt proteinuria. Patients were divided into two groups according to their baseline serum Lp(a) level. Group 1 had Lp(a) levels < or =30 mg/dl (n = 40) and group 2 had Lp(a) levels >30 mg/dl (n = 41). Patients were followed for 2 years. Progression of diabetic nephropathy was defined as a greater than twofold increase of follow-up serum creatinine concentration from the baseline value.

RESULTS

At baseline and during the follow-up, there was no difference in HbA(1c) and lipid profile between groups 1 and 2. However, serum creatinine was significantly higher in group 2 than in group 1 after 1 year (148.3 +/- 78.0 vs. 108.1 +/- 34.9 micromol/l, P = 0.004) and after 2 years (216.9 +/- 144.5 vs. 131.3 +/- 47.3 micromol/l, P = 0.001), although baseline serum creatinine did not differ significantly between groups. In all, 13 of 14 patients with progression of diabetic nephropathy (progressors) were from group 2. Baseline Lp(a) levels were higher in the progressors than in the nonprogressors (62.9 +/- 26.7 vs. 33.5 +/- 27.5 mg/dl, P < 0.001). Multiple logistic regression showed that baseline Lp(a) level was a significant and independent predictor of the progression of diabetic nephropathy.

CONCLUSIONS

Our study demonstrated that Lp(a) is an independent risk factor for the progression of diabetic nephropathy in type 2 diabetic patients with overt proteinuria.

Lipoprotein(a), apolipoprotein(a) polymorphism and coronary atherosclerosis severity in type 2 diabetic patients

BACKGROUND

Few and conflicting data are available in the literature on the association between Lp(a) levels and the severity of coronary artery disease (CAD) in diabetic patients. In addition, no studies took into account the role of apo(a) polymorphism. The purpose of the present study was to analyse the association of the degree of coronary atherosclerosis with Lp(a) levels and apo(a) polymorphism in a large group of type 2 diabetic patients.

METHODS

The study population consisted of 227 consecutive type 2 diabetic patients undergoing a routine coronary angiography to evaluate chest pain or suspected CAD. The patients were subdivided into four subgroups according to the number of coronary arteries diseased: normal arteries (n=26), mono-vessel disease (n=67), bi-vessel disease (n=54) and multi-vessel disease (n=80).

RESULTS

Lp(a) levels (normal arteries: 14.6+/-19.6 mg/dl; mono-vessel disease: 19.0+/-16.4 mg/dl; bi-vessel disease: 19.3+/-15.1 mg/dl; multi-vessel disease: 26.5+/-16.8 mg/dl; p<0.001) and the percentages of patients with at least one isoform of low molecular weight (normal arteries: 23.1%; mono-vessel disease: 38.8%; bi-vessel disease: 75.9%; multi-vessel disease: 81.2%; p<0.001) were significantly correlated with increasing number of coronary vessels diseased. Multiple logistic regression analysis showed that both Lp(a) levels (OR: 1.31; 95% CI: 1.02-4.11) and apo(a) polymorphism (OR: 3.43; 95% CI: 1.67-7.05) were independent predictors of CAD severity.

CONCLUSIONS

Our data suggest that Lp(a) levels and apo(a) polymorphism may be reliable predictors of CAD severity in type 2 diabetic patients.

Relation of apolipoprotein(a) size to alzheimer's disease and vascular dementia

Lipoprotein(a) [Lp(a)] level is a newly established vascular risk factor which has been suggested to play a role in dementia. However, the majority of Lp(a) cell-to-cell interactions are mediated by its specific apolipoprotein(a) [apo(a)] moiety. This suggests that the size polymorphism of apo(a) may be of importance in conveying the Lp(a)-related risk. Specifically, we postulated that variation in apo(a) isoform size may lead to increased risk of vascular dementia (VaD), Alzheimer's disease (AD), stroke, or all three of them. Under a case-control design we compared Lp(a) plasma levels and the distribution of apo(a) phenotypes in groups of subjects consisting of 50 VaD patients, 162 sporadic AD patients, 95 non-demented stroke patients (NDS), and 105 normal controls. The prevalence of small-sized apo(a) isoforms in the VaD group was significantly higher than that in the stroke and normal control groups, with an odds ratio of 5.29 (95% CI 2.24-12.49, p = 0.0001) for the development of VaD for individuals with at least one apo(a) isoform of low molecular weight (LMW). Furthermore, the possession of at least one small-sized apo(a) isoform significantly increased the risk of AD to 1.92 (95% CI 1.02-3.61, p = 0.0434). Our results demonstrate that possession of at least one LMW apo(a) isoform is significantly associated with dementia and specifically offer new evidence of a strong association between the lipoprotein system and post-stroke dementia.

Significance of apolipoprotein(a) phenotypes in acute coronary syndromes: relation with clinical presentation

BACKGROUND

High lipoprotein(a) [Lp(a)] levels and small-sized apolipoprotein(a) [apo(a)] phenotypes have been linked to acute coronary syndromes (ACS). We sought to determine whether Lp(a) concentrations and apo(a) phenotypes may be related to the clinical syndrome of presentation among ACS patients.

METHODS

Two hundred ten ACS patients and 105 controls were enrolled. One hundred thirteen patients presented with acute myocardial infarction (AMI) and 97 with unstable angina pectoris (UAP). Lp(a) concentrations were determined by ELISA and apo(a) isoforms were detected with a high-resolution immunoblotting method.

RESULTS

Lp(a) levels and the percentage of subjects with at least one small-sized apo(a) isoform were significantly higher both in AMI patients and in UAP subjects as compared with controls. Among ACS patients, the percentage of subjects with at least one small apo(a) phenotype was significantly higher in patients who presented with AMI than in those with UAP (p<0.001). Multivariate logistic regression analysis showed that the presence of at least one small-sized apo(a) isoform was associated with AMI as the patient's clinical syndrome of presentation (OR=2.51, 95% CI: 1.38-4.58, p<0.01).

CONCLUSIONS

Among ACS patients, apo(a) isoforms of low molecular weight were associated with AMI onset. High-resolution apo(a) phenotyping might be helpful to identify individuals at high risk for developing AMI.

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.

Lipoprotein(a), apolipoprotein(a) polymorphism and restenosis after intracoronary stent placement in Type 2 diabetic patients

The relationship between lipoprotein(a) [Lp(a)] and restenosis after intracoronary stent implantation has never been analysed in diabetic patients. The aim of the present prospective study was to evaluate whether Lp(a) levels and apolipoprotein(a) [apo(a)] phenotypes are predictors of restenosis after elective stent implantation in Type 2 diabetic patients with de novo lesions of coronary arteries. We recruited 102 Type 2 diabetic patients with a new lesion successfully treated with elective placement of one or two Palmaz-Schatz stents. Follow-up angiography was scheduled at 6 months or earlier if clinically indicated. Seven patients were lost to the follow up. Among 95 patients enrolled, restenosis was present in 37 (38.9%) and absent in 58 (61.1%). The restenosis group showed Lp(a) levels higher than the nonrestenosis group (25.1+/-14.4 vs. 21.3+/-14.6 mg/dl), but the difference was not significant. The restenosis group had a percentage of subjects with at least one apo(a) isoform of low molecular weight (MW) significantly greater than the nonrestenosis group (75.7% vs. 55.1%; P<.05). A multiple logistic regression analysis showed that presence of multivessel disease (risk relative [RR]: 5.83; 95% confidence interval [CI]: 1.21-28.15; P<.05) was the only predictor of restenosis after stent placement in diabetic patients. Lp(a) and apo(a) polymorphisms did not enter the model as predictive variables. Our study shows that the presence of multivessel disease is a predictor of restenosis after intracoronary stent implantation in diabetic patients. On the contrary, Lp(a) and apo(a) polymorphisms do not appear to be reliable markers of restenosis in patients with Type 2 diabetes mellitus.

Silent coronary artery disease in type 2 diabetes mellitus: the role of Lipoprotein(a), homocysteine and apo(a) polymorphism

BACKGROUND

There is little data on the relationship between novel cardiovascular risk factors and silent coronary artery disease (CAD) in diabetic patients. We investigated whether Lipoprotein(a), homocysteine and apolipoprotein(a) polymorphism are associated with angiographically assessed asymptomatic coronary artery disease (CAD) in diabetic patients.

METHODS

1,971 type 2 diabetic patients without clinical signs of cardiovascular diseases and with a negative history of CAD were consecutively evaluated. Among them, 179 patients showed electrocardiographic abnormalities suggestive of ischemia or previous asymptomatic myocardial infarction. These 179 patients were subjected to a non-invasive test for CAD (ECG stress testing and/or scintigraphy). Among patients with a highly positive stress testing (n = 19) or a positive scintigraphy (n = 74), 75 showed an angiographically documented CAD (CAD group). Seventy-five patients without CAD (NO CAD group) were matched by age, sex and duration of diabetes to CAD patients. In NO CAD patients an exercise ECG test, a 48-hour ambulatory ECG and a stress echocardiogram were negative for CAD.

RESULTS

Lipoprotein(a) levels (22.0 +/- 18.9 versus 16.0 +/- 19.4 mg/dl; p < 0.05), homocysteine levels (13.6 +/- 6.6 versus 11.4 +/- 4.9 mmol/l; p < 0.05) and the percentage of subjects with at least one small apolipoprotein(a) isoform (70.7% versus 29.3%; p < 0.0001) were higher in CAD than NO CAD group. Logistic regression analysis showed that apolipoprotein(a) polymorphism (OR:8.65; 95%CI:3.05-24.55), microalbuminuria (OR:6.16; 95%CI:2.21-17.18), smoking (OR:2.53; 95%CI:1.05-6.08), HDL (OR:3.16; 95%CI:1.28-7.81), homocysteine (OR:2.25; 95%CI:1.14-4.43) and Lipoprotein(a) (OR:2.62; 95%CI:1.01-6.79) were independent predictors of asymptomatic CAD.

CONCLUSIONS

The present investigation shows an independent association of Lipoprotein(a), homocysteine and apo(a) polymorphism with silent CAD. Other studies are needed to establish whether these parameters are suitable for CAD screening in diabetic patients.

Assessment of asymptomatic coronary artery disease in apparently uncomplicated type 2 diabetic patients: a role for lipoprotein(a) and apolipoprotein(a) polymorphism

OBJECTIVE

In patients with uncomplicated diabetes, there is low probability of finding significant coronary artery disease (CAD) by noninvasive tests. Therefore, screening for its presence is not justified, and it is important to find reliable predictors of silent CAD to identify patients with uncomplicated diabetes for further screening. The relationship between lipoprotein(a) [Lp(a)], apolipoprotein(a) [apo(a)] polymorphism, and silent CAD has never been studied. We investigated the association of Lp(a) and apo(a) polymorphism with angiographically documented asymptomatic CAD in type 2 diabetic patients without evident complications.

RESEARCH DESIGN AND METHODS

A total of 1,323 diabetic patients without any clinical and electrocardiographic evidence of CAD were evaluated. Of 121 patients with highly positive results of exercise electrocardiography (ECG) (n = 30) or positive results on exercise thallium scintigraphy (n = 91), 103 subjects showed angiographically documented CAD (CAD group). Of 1,106 patients with negative results on exercise ECG, 103 subjects without CAD (NO CAD group) were selected and matched by age, gender, and duration of diabetes to patients in the CAD group. In patients in the NO CAD group, results of exercise ECG, 48-h ambulatory ECG, and stress echocardiography were negative for CAD.

RESULTS

The CAD group had higher Lp(a) levels (21.7 +/- 17.7 vs. 15.2 +/- 19.0 mg/dl; P = 0.0093) than the NO CAD group, and a percentage of subjects had at least one small apo(a) isoform (68.9 vs. 29.1%; P = 0.0000) higher than the NO CAD group. Logistic regression analysis showed that apo(a) phenotypes (odds ratio [OR] 8.13, 95% CI 3.65-21.23), microalbuminuria (5.38, 2.44-11.88), smoking (2.72, 1.31-5.64), and Lp(a) levels (2.41, 1.15-5.03) were predictors of asymptomatic CAD.

CONCLUSIONS

Our investigation reports the first evidence of an independent association of Lp(a) and apo(a) polymorphism with asymptomatic CAD. This suggests that Lp(a) levels and apo(a) phenotypes could be used together with other risk factors as markers of asymptomatic CAD in patients with diabetes.