A potential role of apolipoprotein B in the risk stratification of diabetic patients with dyslipidaemia

The association between the apolipoprotein A1/ high density lipoprotein -cholesterol and diabetes in Taiwan - a cross-sectional study

BACKGROUND

Traditional lipid indices have been associated with type 2 diabetes, but it remains uncertain which lipid index is the best discriminator for diabetes. In this study, we aimed to assess lipoproteins, traditional lipid variables, and other variables to discover their association with diabetes in the Taiwanese population.

METHODS

Data from a nationwide cross-sectional population-based survey of 3087 men and 3373 women in 2002 were analyzed in this study. All participants were assessed for anthropometry, glycosylated hemoglobin, fasting sugar and lipid profiles with triglycerides, high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), and apolipoprotein A1 (ApoA1) and B (ApoB). The ratio of LDL-C/HDL-C, ApoB/ApoA1, ApoB/LDL-C and ApoA1/HDL-C and other variables were analyzed to determine their potential roles in type 2 diabetes in the Taiwanese population. The Odds ratios (ORs) of the risk variables for diabetes were estimated using logistic regression and were adjusted for confounding factors.

RESULTS

The increased ratio of ApoA1/HDL-C was significantly associated with diabetes in men (top tertile vs. lowest: OR 2.98; 95% CI: 1.12 - 7.92; P-trend = 0.030) and women (top tertile vs. lowest: OR 2.15; 95% CI: 1.00 - 4.59; P-trend = 0.047). A modest increased diabetic risk was evident with ApoB/LDL-C in women (top tertile vs. lowest: OR 2.03; 95% CI: 1.07- 3.85; P-trend = 0.028), but not in men (top tertile v. lowest: OR 1.69; 95% CI: 0.79- 3.62; P-trend = 0.198).

CONCLUSIONS

ApoA1/HDL-C had a significant linear association with diabetes in both sexes and was superior to other lipid and lipoprotein variables among the general Taiwanese population.

Low Prevalence of Elevated ApoB Levels in Patients with Type 2 Diabetes Not Receiving Lipid-Lowering Therapy

OBJECTIVE

Cardiovascular disease (CVD) is the leading cause of death in people with type 2 diabetes. Apolipoprotein B (apoB) is known to be a better marker of CVD risk than low-density lipoprotein cholesterol (LDL-C). This study investigated apoB levels in people with type 2 diabetes.

METHODS

We obtained blood samples from 507 consenting people with type 2 diabetes who were not receiving lipid-lowering medication and who had no previous history of CVD. Subjects were divided into 3 groups: men (M), women <50 years old (W1) and women ≥50 years old (W2). Primary analysis examined lipid parameters, specifically apoB. Secondary analysis involved classifying patients according to the Canadian Diabetes Association's apoB, LDL-C and triglyceride (TG) targets.

RESULTS

We found a total mean apoB level of 0.92 g/L. Among patients who failed to achieve the LDL-C target, 28% of M, 39% of W1 and 30% of W2 met the apoB target. The proportions of individuals categorized as being above the LDL-C and apoB targets were significantly different in all 3 groups (p<0.01). When LDL-C was below target and TG was <1.5 mmol/L, 100% of M and W1 and 93% of W2 met the apoB target.

CONCLUSIONS

The discordance between the proportions of patients meeting LDL-C and apoB targets may lead to patients being erroneously classified. ApoB and LDL-C correlate very well when TG is <1.5 mmol/L, but not when ≥1.5 mmol/L. Approximately one-third of patients met both LDL-C and apoB goals. Thus, not all patients with type 2 diabetes should be considered to be at a high risk of CVD.

ApolipoproteinA1-75 G/A (M1-) polymorphism and lipoprotein(a); anti- vs. pro-Atherogenic properties

BACKGROUND

ApolipoproteinA1 (apoA1) is the major apoprotein constituent of high-density-lipoprotein(HDL). The relationship of apoA1 -75 bp(M1-) allele polymorphism with lipoprotein phenotype and cardiovascular disease (CVD) remain unclear. Overnight fasting blood samples were collected from a cohort of high-risk Omani population, 90 non-diabetic subjects and 149 type 2 diabetes mellitus (T2DM) subjects for genotype and phenotype studies.

RESULTS

The M1+ and M1- alleles frequencies were 0.808 and 0.192 for M1+ and M1-, respectively, comparable to the frequency of apoA1 (M1+ and M1-) amongst a healthy Omani population, 0.788 and 0.212, respectively. The frequencies of the hetero- and homozygous subjects for the MspI polymorphism at -75 (M1-) of the apoA1 gene were in Hardy-Weinberg equilibrium. The mean Lp(a) concentration was significantly higher(P = 0.02) in subjects carrying M1- allele compared to M1+ allele of the APOA1 gene with an odd ratio of 2.3(95% CI, 1.13-14.3), irrespective of gender and the diabetic status.

CONCLUSION

ApolipoproteinA1-75 G/A (M1-) polymorphism is relatively common and is positively associated with Lp(a) and therefore, may confer a potential risk for cardiovascular disease (CVD).

Apolipoprotein B as a long-term predictor of mortality in type 1 diabetes mellitus: a 15-year follow up

OBJECTIVES

To evaluate the association of apolipoprotein B (apo B) with mortality due to all causes, to cardiac disease and to ischaemic heart disease (IHD) in subjects with type 1 diabetes mellitus.

SUBJECTS

165 subjects with type 1 diabetes included in the Swiss Cohort of the WHO Multinational Study of Vascular Disease in Diabetes were followed for 14.7+/-0.45 years.

METHODS

Causes of death were obtained from death certificates, hospital records and postmortem reports. Using a parametric proportional hazards model the association of apo B with mortality rates was assessed by time-to-event analysis, including the absolute cumulative mortality risk over time for various apo B levels at baseline.

RESULTS

Apo B was positively associated with all-cause mortality [hazard ratio (HR) 2.65 per g L-1 increase of apo B, 95% CI: 1.11-6.36, P=0.029], cardiac mortality (HR 11.64, 1.03-131.11, P=0.047) and IHD mortality (HR 9.36, 1.26-69.66, P=0.029). An apo B>or=0.96 g L-1 translated into a duplication of overall mortality hazard (HR 1.93, 1.00-3.72, P=0.050), and a sevenfold increase of mortality because of cardiac disease or IHD (HR 7.44, 1.44-38.42, P=0.017 and HR 7.38, 0.78-69.82, P=0.081). A baseline apo B of 1.5 g L-1 predicted an absolute cumulative risk to die over the next 10 years of 12.1% (5.2-31.7) for male and of 10.4% (4.7-26.1) for female subjects whereas risks were 6.3% (1.8-21.4) and 5.4% (0.8-15.8) for an apo B of 0.8 g L-1.

CONCLUSION

Apo B is consistently associated with an increased mortality in type 1 diabetes.

The apoB/apoA-I ratio: a strong, new risk factor for cardiovascular disease and a target for lipid-lowering therapy--a review of the evidence

During the last several years interest has focused on the importance of the lipid-transporting apolipoproteins--apoB transports all potentially atherogenic very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL) and LDL particles, and apoA-I transports and acts as the major antiatherogenic protein in the HDL particles. The evidence for the apoB/apoA-I ratio being a strong, new risk factor for cardiovascular (CV) disease and a target for lipid-lowering therapy is reviewed. Results from clinical prospective studies and lipid-lowering trials in healthy subjects and in patients with different clinical manifestations of atherosclerosis are reported. Risk of nonfatal and fatal myocardial infarction and stroke, and manifestations of atherosclerosis documented by angiographic, ultrasound and other techniques has been related to conventional lipids and apolipoproteins (apo). The cholesterol balance determined as the apoB/apoA-I ratio has repeatedly been shown to be a better marker than lipids, lipoproteins and lipid ratios. The results indicate that the apoB/apoA-I ratio is a simple, accurate and new risk factor for CV disease--the lower the apoB/apoA-I ratio, the lower is the risk. Guidelines should be developed in order to recognize the important clinical risk information embedded in the apoB/apoA-I ratio.

Atherogenic dyslipidemia associated with metabolic syndrome and insulin resistance

Atherogenic dyslipidemia, a component of metabolic syndrome, is characterized by high levels of apolipoprotein B (apo B)-containing lipoproteins, including very-low-density lipoprotein remnants and small low-density lipoprotein particles, and reduced levels of high-density lipoprotein cholesterol. Although the National Cholesterol Education Program Adult Treatment Panel III includes elevations in blood pressure and plasma glucose in the definition of metabolic syndrome, the broader scope of metabolic syndrome includes proinflammatory and prothrombotic states, which derive from the secretory activity of adipose tissue. Abdominal fat can adversely affect insulin action and the disposal of glucose through an increase in the release of free fatty acid, resulting in accumulation of triglyceride in muscle and liver, thereby depressing insulin action and increasing output of apo B-containing lipoproteins. Impaired regulation of adipokines, bioactive substances secreted from adipose tissue, likely produces systemic inflammation, which can promote atherogenesis. Insulin resistance is recognized as an important metabolic defect linking the components of metabolic syndrome. One molecule that may play an important role in metabolic syndrome to regulate metabolic and vascular pathways is the peroxisome proliferator-activated receptor-gamma (PPAR-gamma). Studies have established PPAR-gamma deficiency as a cause of lipodystrophy and confirmed its adipogenic role. Patients with atherogenic dyslipidemia and metabolic syndrome should undergo global risk assessment for cardiovascular disease and future cardiovascular events to determine an overall treatment strategy.