Relationship of Apolipoprotein B Levels to the Number of Risk Factors for Metabolic Syndrome

Metabolic syndrome update

The metabolic syndrome is a multiplex risk factor for atherosclerotic cardiovascular disease and type 2 diabetes. It is composed of atherogenic dyslipidemia, elevated blood pressure, insulin resistance and elevated glucose, a pro-thrombotic state, and a pro-inflammatory state. Excess energy intake and concomitant obesity are the major drivers of the syndrome. Lifestyle intervention can reverse metabolic risk factors, but at times, drug therapies or bariatric surgery may be required to control more overt risk factors.

Association of apolipoprotein B and nuclear magnetic resonance spectroscopy-derived LDL particle number with outcomes in 25 clinical studies: assessment by the AACC Lipoprotein and Vascular Diseases Division Working Group on Best Practices

BACKGROUND

The number of circulating LDL particles is a strong indicator of future cardiovascular disease (CVD) events, even superior to the concentration of LDL cholesterol. Atherogenic (primarily LDL) particle number is typically determined either directly by the serum concentration of apolipoprotein B (apo B) or indirectly by nuclear magnetic resonance (NMR) spectroscopy of serum to obtain NMR-derived LDL particle number (LDL-P).

CONTENT

To assess the comparability of apo B and LDL-P, we reviewed 25 clinical studies containing 85 outcomes for which both biomarkers were determined. In 21 of 25 (84.0%) studies, both apo B and LDL-P were significant for at least 1 outcome. Neither was significant for any outcome in only 1 study (4.0%). In 50 of 85 comparisons (58.8%), both apo B and LDL-P had statistically significant associations with the clinical outcome, whereas in 17 comparisons (20.0%) neither was significantly associated with the outcome. In 18 comparisons (21.1%) there was discordance between apo B and LDL-P.

CONCLUSIONS

In most studies, both apo B and LDL-P were comparable in association with clinical outcomes. The biomarkers were nearly equivalent in their ability to assess risk for CVD and both have consistently been shown to be stronger risk factors than LDL-C. We support the adoption of apo B and/or LDL-P as indicators of atherogenic particle numbers into CVD risk screening and treatment guidelines. Currently, in the opinion of this Working Group on Best Practices, apo B appears to be the preferable biomarker for guideline adoption because of its availability, scalability, standardization, and relatively low cost.

Metabolic risk susceptibility in men is partially related to adiponectin/leptin ratio

BACKGROUND

High adiponectin/leptin ratio may be protective from metabolic risks imparted by high triglyceride, low HDL, and insulin resistance.

METHODS

This cross-sectional study examines plasma adipokine levels in 428 adult men who were subgrouped according to low (<6.5  μ g/mL)and high (≥6.5  μ g/mL)adiponectin levels or a low or high ratio of adiponectin/leptin.

RESULTS

Men with high adiponectin/leptin ratio had lower plasma triglyceride and higher HDL cholesterol than those with low ratio. Similarly, those with high adiponectin/leptin ratio had lower TG/HDL cholesterol ratio and HOMA2-IR than those with low ratio. In contrast, levels of adiponectin or the ratio of adiponectin/leptin did not associate with systolic blood pressure. But the ratio of adiponectin/leptin decreased progressively with the increase in the number of risk factors for metabolic syndrome.

CONCLUSION

Adipokine levels may reflect adipose tissue triglyceride storage capacity and insulin sensitivity. Leptin is an index of fat mass, and adiponectin is a biomarker of triglyceride metabolism and insulin sensitivity. Men with high adiponectin/leptin ratios have better triglyceride profile and insulin sensitivity than men with a low ratio regardless of waist girth.

Comparisons of apolipoprotein B levels estimated by immunoassay, nuclear magnetic resonance, vertical auto profile, and non-high-density lipoprotein cholesterol in subjects with hypertriglyceridemia (SAFARI Trial)

Low-density lipoprotein (LDL) cholesterol and triglyceride-rich lipoproteins constitute non-high-density lipoprotein (non-HDL) cholesterol. These are atherogenic lipoproteins and non-HDL cholesterol is a secondary target of treatment beyond LDL cholesterol in patients with hypertriglyceridemia. Some investigators favor total apolipoprotein B over non-HDL cholesterol as the secondary target of treatment. This is based on publications suggesting that total apolipoprotein B is more predictive of cardiovascular events than non-HDL cholesterol. Several methods are available for estimating total apolipoprotein B. This study compared total apolipoprotein estimated by immunonephelometric assay (INA), vertical auto profile (VAP), nuclear magnetic resonance (NMR), and non-HDL cholesterol levels in patients with hypertriglyceridemia from the previously reported Simvastatin plus Fenofibrate for Combined Hyperlipidemia (SAFARI) trial. Total apolipoprotein B levels were found to be highest by INA, intermediate by NMR and non-HDL cholesterol, and lowest by VAP. Concordance for non-HDL cholesterol levels among the INA, VAP, and NMR methods was better than that for total apolipoprotein B levels; the correlation between non-HDL cholesterol and apolipoprotein B by INA was strongest (0.929). In patients with a low triglyceride/HDL cholesterol ratio (<3.5), total apolipoprotein B determined by INA was higher than that estimated from non-HDL cholesterol levels, whereas in patients with a high triglyceride/HDL C ratio (≥3.5), apolipoprotein B predicted using non-HDL cholesterol was in better agreement with INA-determined apolipoprotein B levels. Similar trends were observed with VAP using equations specific for LDL particle size. In conclusion, more work is needed to improve agreement of apolipoprotein B measurements among methods employed clinically. Non-HDL cholesterol is also useful to predict total apolipoprotein B and some improvement may be attained by taking into account the ratio of triglyceride/HDL cholesterol as a measurement of LDL particle size.

Gender-based cardiometabolic risk evaluation in minority and non-minority men grading the evidence of non-traditional determinants of cardiovascular risk

Evaluation of cardiometabolic risk has become vital in primary prevention of adverse vascular events (coronary artery disease, heart attack, stroke or congestive heart failure), particularly in younger middle-aged men (40-60 years old). To discern the prevalence of events in these men, clinicians often stratify cardiovascular risk and treat according to traditional Framingham risk criteria. Yet it is evident that the traditional Framingham risk assigned to intermediate- and low-risk men will miss several of these individuals deemed at high 'cardiometabolic risk', also known as residual cardiovascular risk. This review will elaborate the definition of cardiometabolic risk and apply the use of surrogate markers for cardiovascular risk stratification in men in addition to the traditional Framingham-based markers. It will utilise both gender non-specific and gender-specific determinants of cardiometabolic risk. Lastly, it will examine minority men's health and racial differences in these determinants of cardiovascular risk. This analysis includes an electronic literature search utilising PubMed, EMBASE and MEDLINE databases to clarify the level of evidence for the stepwise utility of novel biomarkers for cardiometabolic risk in the male patient. This manuscript generates discussion of the utility of markers of cardiometabolic risk stratification. The following questions are summarised: (i) Are there non-traditional tests that might define this risk better than traditional markers? (ii) Will treatment based on this risk assessment augment present risk stratification and lower cardiovascular risk? (iii) What is known regarding racial differences surrounding cardiometabolic risk assessment? Traditional risk factors including Framingham Risk Score underestimate the overall 10 year and lifetime risk for the intermediate-risk younger middle-aged men<60 years of age. This fact is especially true in the minority population. We have graded the evidence of non-gender specific and gender-specific markers of cardiometabolic risk, thereby, allowing greater clarification of risk in this population. The pragmatic use of these novel markers of cardiometabolic risk may help stratify those individuals at greater lifetime risk than that noted by the Framingham Risk Score.

Apolipoprotein B and non-high-density lipoprotein cholesterol are better risk markers for coronary artery disease than low-density lipoprotein cholesterol in hypertriglyceridemic metabolic syndrome patients

BACKGROUND

Metabolic syndrome is highly prevalent in the general population. Small dense low-density lipoprotein (sd-LDL) particles have been considered as a risk marker in metabolic syndrome diagnosis. Apolipoprotein B (ApoB) concentration reflects the number of LDL particles and is closely associated with atherosclerosis. The aim of this study was to compare the associations of ApoB, non-high-density lipoprotein cholesterol (NHDL-C), and low-density lipoprotein cholesterol (LDL-C) with metabolic syndrome and its relationship with significant coronary stenosis (SCS) in a Tunisian population.

METHODS

We enrolled 192 patients, who underwent coronary angiography. The body mass index, blood lipids, fasting glucose, insulin concentration, and blood pressure of every patient were measured. Metabolic syndrome was diagnosed according to the International Diabetes Federation criteria.

RESULTS

The frequency of metabolic syndrome was 58.3%. The comparison of the lipidic parameters between subject with and without metabolic syndrome showed a significant increase in ApoB and NHDL-C but not in LDL-C. By considering triglyceride (TG) limits (TG ≤ 0.9 mmol/L and TG > 1.70 mmol/L), we noted no differences in ApoB, NHDL-C, and LDL-C between subjects with and without metabolic syndrome in triglyceridemia ≤0.9 mmol/L. In triglyceridemia >1.70 mmol/L, a significant increase in ApoB and NHDL-C, but not in LDL-C, was noted. These results seem to consolidate the probability of increased sd-LDL in hypertriglyceridemic metabolic syndrome subjects. Indeed, in our study the odds ratio (OR) of SCS associated with metabolic syndrome is 3.81 (P = 0.007) in the studied population. This risk increases to 8.70 (P = 0.026) in hypertriglyceridemic subjects and seems to be associated with ApoB and NHDL-C (OR = 1.87, P = 0.038; OR = 1.26, P = 0.048).

CONCLUSIONS

This study suggests that ApoB and NHDL-C seem to be more correlated to SCS in metabolic syndrome with hypertriglyceridemia than LDL-C.

Correlation of non-high-density lipoprotein cholesterol and low-density lipoprotein cholesterol with apolipoprotein B during simvastatin + fenofibrate therapy in patients with combined hyperlipidemia (a subanalysis of the SAFARI trial)

Guidelines have recommended non-high-density lipoprotein (non-HDL) cholesterol as a secondary target for therapy after the low-density lipoprotein (LDL) cholesterol goals have been met in patients with hypertriglyceridemia; non-HDL cholesterol is viewed as a surrogate for apolipoprotein (Apo)B, an alternate end point of treatment. The present analysis of the previously reported Simvastatin plus Fenofibrate for Combined Hyperlipidemia (SAFARI) trial assessed the associations of non-HDL cholesterol and LDL cholesterol with ApoB levels in patients with combined hyperlipidemia treated with combination simvastatin (20 mg) and fenofibrate (160 mg) or simvastatin monotherapy (20 mg). The correlations of these factors were analyzed in the overall modified intent-to-treat population (n = 594) and in patient subgroups stratified by triglyceride (TG) tertiles. Simvastatin plus fenofibrate and simvastatin alone significantly reduced LDL cholesterol, TG, non-HDL cholesterol and ApoB levels and non-HDL cholesterol/ApoB ratio (p < or =0.0004), regardless of the TG level. The greatest reductions occurred with combination treatment. The baseline levels of non-HDL cholesterol and LDL cholesterol correlated highly with ApoB and were stronger in the lower TG tertiles than in the higher TG tertiles. After 12 weeks, the correlations had changed little with simvastatin monotherapy but had increased substantially with combination therapy and were most improved at high TG levels. In conclusion, these results suggest that both non-HDL cholesterol and ApoB provide similar information in relation to treatment response in patients with combined hyperlipidemia and hypertriglyceridemia, and that non-HDL cholesterol is a good indicator of ApoB-containing lipoproteins, supporting its recommended use as a secondary therapeutic target in these patients.

Effect of ezetimibe/simvastatin vs atorvastatin on lowering levels of LDL-C and non-HDL-C, ApoB, and hs-CRP in patients with type 2 diabetes

BACKGROUND

In addition to low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), apolipoprotein B (ApoB), and high-sensitivity C-reactive protein (hs-CRP) are considered predictive for cardiovascular disease in type 2 diabetes mellitus (T2DM) patients.

OBJECTIVE

To assess the proportion of T2DM patients with hypercholesterolemia who attained the optional target level of LDL-C (<70 mg/dL) and additionally non-HDL-C (<100 mg/dL), ApoB (<90 mg/dL), and hs-CRP (<2 mg/L), following treatment with ezetimibe/simvastatin (E/S) vs atorvastatin (A).

METHODS

This post-hoc analysis of a multicenter, randomized, double-blind, 6-week parallel study assessed the proportion of T2DM patients who attained specified LDL-C levels and non-HDL-C, ApoB, and hs-CRP with usual, recommended starting doses of E/S (10/20 mg) vs A (10 or 20 mg) and next highest doses of E/S (10/40 mg) vs A (40 mg) by logistic regression. Baseline triglyceride and hs-CRP effects were also evaluated.

RESULTS

Significantly higher percentages of patients treated with E/S compared to A achieved individual and concurrent target levels of LDL-C (<70 mg/dL), non-HDL-C (<100 mg/dL), and ApoB (<90 mg/dL) at all dose comparisons (P < 0.05 to P < 0.001). Baseline triglyceride levels had no effect on reaching LDL-C levels. Attainment of non-HDL-C (<100 mg/dL), and ApoB (<90 mg/dL) was lower at triglycerides ≥200 mg/dL than <200 mg/dL. Achievement of hs-CRP level (<2 mg/L) was comparable for both treatments. Significantly more patients attained both LDL-C (<70 mg/dL) and hs-CRP (<2 mg/L) at all E/S doses compared to A (P < 0.05 to P < 0.001), regardless of baseline CRP levels.

CONCLUSION

E/S provides a therapeutic option to T2DM patients for lowering not only LDL-C, but also non-HDL-C, ApoB, and hs-CRP. These factors may help guide assessment and treatment of cardiovascular disease risk in these patients.