Risk factors for coronary disease: the time for a paradigm shift?

Association between hypertriglyceridemia and protein oxidation and proinflammatory markers in normocholesterolemic and hypercholesterolemic individuals

BACKGROUND

Although hypercholesterolemia is a well-established risk factor for coronary heart disease, evidence suggests that increased triglyceride (TG) concentrations are also an independent risk factor. TG concentrations >150mg/dl are observed nearly twice as often in subjects with atherosclerosis. We assessed the association between hypertriglyceridemia and protein oxidation and proinflammatory markers in normocholesterolemic and hypercholesterolemic individuals.

METHODS

We included 127 volunteers enrolled in Cruz Alta, RS, Brazil. The patients were stratified based on total cholesterol and TG concentrations for analysis of associations with inflammation (high-sensitivity C-reactive protein - hs-CRP), endothelial dysfunction (nitric oxide - NOx) and oxidative stress (advanced oxidation protein products - AOPPs; ischemia-modified albumin - IMA). Correlations between variables were determined and multiple regression analysis was employed to investigate whether some variables correlate with TG concentrations.

RESULTS

Hypertriglyceridemia was related to oxidative stress and proinflammatory markers in individuals independent of total cholesterol concentrations. Moreover, the results indicate a stronger association of tested biomarkers with TG concentrations than with total cholesterol. The results indicate a positive correlation between oxidative stress and TG concentrations in the sera of hypercholesterolemia subjects. AOPPs and IMA concentrations were associated with the presence of hypertriglyceridemia in a manner that was independent of age, gender, hypertension and diabetes mellitus disease, smoking habits, sedentary lifestyle, BMI, waist circumference, LDL, HDL and total cholesterol concentrations.

CONCLUSIONS

We speculate that TG concentrations can reflect the enhancement of protein oxidation and proinflammation.

Apolipoprotein A-I: insights from redox proteomics for its role in neurodegeneration

Proteomics has a wide range of applications, including determination of differences in the proteome in terms of expression and post-translational protein modifications. Redox proteomics allows the identification of specific targets of protein oxidation in a biological sample. Using proteomic techniques, apolipoprotein A-I (ApoA-I) has been found at decreased levels in subjects with a variety of neurodegenerative disorders including in the serum and cerebrospinal fluid (CSF) of Alzheimer disease (AD), Parkinson disease (PD), and Down syndrome (DS) with gout subjects. ApoA-I plays roles in cholesterol transport and regulation of inflammation. Redox proteomics further showed ApoA-I to be highly oxidatively modified and particularly susceptible to modification by 4-hydroxy-2-trans-nonenal (HNE), a lipid peroxidation product. In the current review, we discuss the consequences of oxidation of ApoA-I in terms of neurodegeneration. ROS-associated chemotherapy related ApoA-I oxidation leads to elevation of peripheral levels of tumor necrosis factor-α (TNF-α) that can cross the blood-brain barrier (BBB) causing a signaling cascade that can contribute to neuronal death, likely a contributor to what patients refer to as "chemobrain." Current evidence suggests ApoA-I to be a promising diagnostic marker as well as a potential target for therapeutic strategies in these neurodegenerative disorders.

Apolipoproteins: metabolic role and clinical biochemistry applications

Lipoprotein metabolism is dependent on apolipoproteins, multifunctional proteins that serve as templates for the assembly of lipoprotein particles, maintain their structure and direct their metabolism through binding to membrane receptors and regulation of enzyme activity. The three principal functions of lipoproteins are contribution to interorgan fuel (triglyceride) distribution (by means of the fuel transport pathway), to the maintenance of the extracellular cholesterol pool (by means of the overflow pathway) and reverse cholesterol transport. The most important clinical application of apolipoprotein measurements in the plasma is in the assessment of cardiovascular risk. Concentrations of apolipoprotein B and apolipoprotein AI (and their ratio) seem to be better markers of cardiovascular risk than conventional markers such as total cholesterol and LDL-cholesterol. Apolipoprotein measurements are also better standardized than the conventional tests. We suggest that measurements of apolipoprotein AI and apolipoprotein B are included as a part of the specialist lipid profile. We also suggest that lipoprotein (a) should be measured as part of the initial assessment of dyslipidaemias because of its consistent association with cardiovascular risk. Genotyping of apolipoprotein E isoforms remains useful in the investigation of mixed dyslipidaemias. Lastly, the role of postprandial metabolism is increasingly recognized in the context of atherogenesis, obesity and diabetes. This requires better markers of chylomicrons, very-low-density lipoproteins and remnant particles. Measurements of apolipoprotein B48 and remnant lipoprotein cholesterol are currently the key tests in this emerging field.

Obesity, glucose intolerance and diabetes and their links to cardiovascular disease. Implications for laboratory medicine

This article provides an overview of the role of metabolite toxicity, low-grade inflammation and disturbed cellular signaling in obesity, glucose intolerance and diabetes. It also highlights links between this continuum of deteriorating glucose tolerance and atherosclerosis. Obesity, diabetes mellitus, and cardiovascular disease are all related to diet and to the level of physical activity. They have reached epidemic proportions worldwide. Glucose intolerance and diabetes increase the risk of atherosclerotic events. Moreover, obesity, and glucose intolerance or diabetes, are components of the metabolic syndrome, which also imparts an increased cardiovascular risk. There is increasing recognition that common mechanisms contribute to diabetes and cardiovascular disease. Following increased calorie intake and/or decreased physical activity, fuel metabolism generates excess of 'toxic' metabolites, particularly glucose and fatty acids. Homeostasis is affected by the endocrine output from the adipose tissue. Reactive oxygen species are generated, creating oxidative stress, which exerts major effects on signaling pathways, further affecting cellular metabolism and triggering low-grade inflammatory reaction. This perspective on the diabetic syndrome has been reflected in the approach to its treatment, which integrates maintenance of glycemic control with primary and secondary cardiovascular prevention. Laboratory medicine should support diabetes care with an integrated package of tests which, in addition to glycemic control, enable assessment and monitoring of the risk of microvascular complications as well as cardiovascular disease.

Appropriateness of cholesterol and triglycerides reporting checked by External Quality Assessment programs

BACKGROUND

The recommendations of the Second Joint Task Force of European and Other Societies on Coronary Prevention and the third Adult Treatment Panel report (ATPIII) released by the National Cholesterol Education Program are based on accumulating evidence concerning the contribution of lipoproteins and other risk factors in the development of coronary heart disease (CHD). The laboratories play an important role in the successful adoption of these guidelines.

METHODS

In External Quality Assessment (EQA) programs managed by the Center of Biomedical Research, results and respective reference intervals (RI) are sent as laboratory's medical form. We assessed how well the 200 participants to EQA scheme 2002 for clinical biochemistry reported total cholesterol (TC) and triglycerides (TGs) results according to either European or National Cholesterol Education Program (NCEP) guidelines.

RESULTS

Only 18% of laboratories reported total cholesterol concentrations correctly in terms of desirable, borderline-high, and high risk for the CHD development, 12% reported a single desirable value (180, 190, or 200 mg/dl), and 70% reported the RI (85 laboratories in the whole interval, 34 are the only upper reference limit and 15 are the desirable value in addition to RI). The upper reference limit was 200 mg/dl in 65% of cases, but 32% of laboratories presented higher limits, reaching values as high as 250-260 mg/dl. Only the 3.7% of laboratories reported triglyceride concentrations in terms of risk-oriented ranges for the CHD development, 6.8% the single desirable value, and 89.5% the RI.

CONCLUSION

Our study demonstrates that the current practice of reporting results for cholesterol and triglycerides does not follow the guidelines, and appropriate changes are required to be made.