Relation among lipoprotein subfractions and carotid atherosclerosis in Alaskan Eskimos (from the GOCADAN Study)

Sphingolipidomic profile and HDL subfractions in obese dyslipidemic type 2 diabetic patients

PURPOSE

The aim of the study was to investigate changes in serum sphingolipid levels and high density lipoprotein (HDL) subtypes with relation to low-density lipoprotein cholesterol (LDL-C), non-HDL-C and triglyceride (TG) levels in type 2 diabetes mellitus (T2DM) patients.

METHODS

Blood was obtained from 60 patients with T2DM. Levels of sphingosine-1-phosphate (S1P), C16-C24 sphingomyelins (SMs), C16-C24 ceramides (CERs), and C16 CER-1 P were determined by LC-MS/MS. Serum concentrations of cholesterol ester transfer protein (CETP), lecithin-cholesterol acyltransferase (LCAT) and apolipoprotein A-1 (apoA-I) were analyzed by enzyme-linked immunosorbent assay (ELISA). HDL subfraction analysis was performed by Disc polyacrylamide gel electrophoresis.

RESULTS

C16 SM, C24 SM, C24-C16 CER and C16 CER-1 P levels were significantly increased in T2DM patients with LDL-C above 160 mg/dL, compared to those with LDL-C below 100 mg/dL. A significant correlation was observed between C24:C16 SM, C24:C16 CER ratios and LDL-C, non HDL-C levels. Higher serum levels of C24 SM, C24-C18 CER and C24:C16 SM ratio was seen in obese T2DM patients (BMI>30) compared to those with BMI 27-30. Patients with fasting TG levels below 150 mg/dL had significantly increased HDL-large and significantly decreased HDL-small fractions compared to those with fasting TG levels above 150 mg/dL.

CONCLUSION

Obese dyslipidemic T2DM patients had increased levels of serum sphingomyelins, ceramides and HDL-small fractions. The ratio of serum C24:C16 SM, C24:C16 CER and long chain CER levels may be used as diagnostic and prognostic indicators of dyslipidemia in T2DM.

Low-density lipoprotein cholesterol-to-apolipoprotein B ratio as a potential indicator of LDL particle size and plasma atherogenicity in type 2 diabetes

AIMS

Atherogenic dyslipidemia, associated with small, dense low-density lipoprotein-cholesterol (S-LDL) particles and impaired metabolism of triglycerides (TGs) and high-density lipoprotein-cholesterol (HDL-c), leads to the development of atherosclerosis-related complications of type 2 diabetes mellitus. Based on the hypothesis that an LDL-c-to-apolipoprotein B ratio (LDL/ApoB) < 1.2 may predict the prevalence of S-LDL, this study aimed to evaluate the LDL/ApoB ratio in patients with type 2 diabetes with moderately elevated TG levels.

METHODS

The study population consisted of 121 outpatients with type 2 diabetes (S-LDL group, LDL/ApoB < 1.2, n = 79; L-LDL group, LDL/ApoB > 1.2, n = 42) and 58 healthy subjects. The LDL/ApoB ratio was calculated from the measured LDL-c and ApoB levels in participants with TG levels lower than 4.5 mmol/L. Since TGs and HDL-c are included in the atherogenic index of plasma (AIP), we evaluated the relationship between LDL/ApoB and the AIP.

RESULTS

Higher levels of AIP, TG (both P < 0.0001), and lipid hydroperoxides (LOOH) (P < 0.001) and lower levels of HDL-c, total cholesterol, and non-HDL-c (P < 0.001, <0.01, <0.05, respectively) were found in the S-LDL group compared to the L-LDL group. There were significant relationships between the LDL/ApoB ratio and the AIP, TG (both P < 0.0001), LOOH (P < 0.0005), and HDL-c levels (P < 0.05) in the S-LDL group.

CONCLUSIONS

The prevalence of S-LDL particles (65%) and the close association of LDL/ApoB with the AIP suggest that this ratio may be a potential indicator of increased cardiovascular risk in patients with type 2 diabetes.

Dietary Fibre as a Unifying Remedy for the Whole Spectrum of Obesity-Associated Cardiovascular Risk

Obesity is a pandemic carrying the heavy burden of multiple and serious co-morbidities including metabolic syndrome, type 2 diabetes and cardiovascular diseases. The pathophysiological processes leading to the accumulation of body fat slowly evolve to fat accumulation in other body compartments than subcutaneous tissue. This abnormal fat deposition determines insulin resistance which in turn causes blood glucose and lipid metabolism derangement, non-alcoholic fatty liver disease, hypertension, and metabolic syndrome. All these conditions contribute to increase the cardiovascular risk of obese people. Several randomized clinical trials demonstrated that moderate weight loss (5⁻10%) in obese patients improves obesity-related metabolic risk factors and coexisting disorders. Therefore, nutritional strategies able to facilitate weight management, and in the meantime positively influence obesity-associated cardiovascular risk factors, should be implemented. To this aim, a suitable option could be dietary fibres that may also act independently of weight loss. The present narrative review summarizes the current evidence about the effects of dietary fibres on weight management in obese people. Moreover, all of the different cardiovascular risk factors are individually considered and evidence on cardiovascular outcomes is summarized. We also describe the plausible mechanisms by which different dietary fibres could modulate cardio-metabolic risk factors. Overall, despite both epidemiological and intervention studies on weight loss that show statistically significant but negligible clinical effects, dietary fibres seem to have a beneficial impact on main pathophysiological pathways involved in cardiovascular risk (i.e., insulin resistance, renin-angiotensin, and sympathetic nervous systems). Although the evidence is not conclusive, this suggests that fibre would be a suitable option to counteract obesity-related cardio-metabolic diseases also independently of weight loss. However, evidence is not consistent for the different risk factors, with clear beneficial effects shown on blood glucose metabolism and Low Density Lipoprotein (LDL) cholesterol while there is fewer, and less consistent data shown on plasma triglyceride and blood pressure. Ascribing the beneficial effect of some foods (i.e., fruits and vegetables) solely to their fibre content requires more investigation on the pathophysiological role of other dietary components, such as polyphenols.

Apolipoprotein B is associated with carotid atherosclerosis progression independent of individual cholesterol measures in a 9-year prospective study of Multi-Ethnic Study of Atherosclerosis participants

BACKGROUND

High blood cholesterol contributes to atherosclerosis, yet reliance on the lipid panel alone may mischaracterize individuals with elevated lipoprotein particle numbers.

OBJECTIVE

The aim of the article was to determine whether elevated lipoprotein or apolipoprotein measures are associated with carotid atherosclerosis and plaque progression independent of cardiovascular (CV) risk factors including standard lipids in a subcohort of 2228 Multi-Ethnic Study of Atherosclerosis participants.

METHODS

Ultrasonography assessed carotid artery plaque and common carotid intima-media thickness (cIMT) at baseline and after a median period of 9.4 years. Nuclear magnetic resonance spectroscopy estimated lipoprotein particle concentrations. Apolipoprotein B (ApoB) and apolipoprotein A-I were measured using an automated immunoassay. Regression analysis determined associations of apolipoprotein and lipoprotein measurements with cIMT and relative risk regression determined associations with carotid plaque progression.

RESULTS

After adjustment for typical CV risk factors, individuals in top quartiles of ApoB, ApoB/apolipoprotein A-I, low-density lipoprotein particles (LDL-P), small LDL-P, and total LDL-P/high-density lipoprotein (HDL) particles showed similar risks of carotid plaque and cIMT progression as LDL-C, non-HDL cholesterol (HDL-C), total cholesterol (TC), and TC/HDL-C. A significant association with plaque progression remained in the top ApoB quartile after further adjustment for LDL-C (P = .02) or TC + HDL-C (P = .04), but was nonsignificant when adjusted for all lipid covariates (P = .086). Those in the top quartile of small LDL-P concentrations showed greater cIMT progression than those in the referent after adjustment for LDL-C, but this was nonsignificant after adjustment for TC + HDL-C.

CONCLUSION

When coupled with evidence that apolipoprotein testing identifies lipid-lipoprotein discordance, these findings suggest that ApoB and small LDL-P provide atherosclerosis risk information that is not revealed by typical CV risk factors.

Nuclear magnetic resonance-determined lipoprotein subclasses and carotid intima-media thickness in type 1 diabetes

BACKGROUND

Dyslipidemia has been linked to vascular complications of Type 1 diabetes (T1DM). We investigated the prospective associations of nuclear magnetic resonance-determined lipoprotein subclass profiles (NMR-LSP) and conventional lipid profiles with carotid intima-media thickness (IMT) in T1DM.

METHODS

NMR-LSP and conventional lipids were measured in a subset of Diabetes Control and Complications Trial (DCCT) participants (n = 455) at study entry ('baseline', 1983-89), and were related to carotid IMT determined by ultrasonography during the observational follow-up of the DCCT, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, at EDIC Year 12 (2004-2006). Associations were defined using multiple linear regression stratified by gender, and following adjustment for HbA1c, diabetes duration, body mass index, albuminuria, DCCT randomization group, smoking status, statin use, and ultrasound devices.

RESULTS

In men, significant positive associations were observed between some baseline NMR-subclasses of LDL (total IDL/LDL and large LDL) and common and/or internal carotid IMT, and between conventional total- and LDL-cholesterol and non-HDL-cholesterol and common carotid IMT, at EDIC Year 12; these persisted in adjusted analyses (p < 0.05). Large LDL particles and conventional triglycerides were positively associated with common carotid IMT changes over 12 years (p < 0.05). Inverse associations of mean HDL diameter and large HDL concentrations, and positive associations of small LDL with common and/or internal carotid IMT (all p < 0.05) were found, but did not persist in adjusted analyses. No significant associations were observed in women.

CONCLUSION

NMR-LSP-derived LDL particles, in addition to conventional lipid profiles, may help in identifying men with T1DM at highest risk for vascular disease.

Dietary grape powder increases IL-1β and IL-6 production by lipopolysaccharide-activated monocytes and reduces plasma concentrations of large LDL and large LDL-cholesterol particles in obese humans

Obese individuals are at an increased risk of developing CVD, hypertension, type 2 diabetes, and bacterial and viral infections when compared with the normal-weight population. In a 9-week randomised, double-blind, cross-over study, twenty-four obese subjects aged between 20 and 60 years and with a BMI between 30 and 45 kg/m2were fed grape or placebo powder for 3-week intervals to determine the effects of dietary grapes on blood lipid profiles, plasma inflammatory marker concentrations and immune cell function. Blood samples were collected on days 1 and 8 for obtaining baseline information and at weeks 3, 4, 8 and 9. Comprehensive chemistry panels, lipid profile analyses by NMR, measurement of plasma inflammatory marker concentrations, and analyses of cytokine production by activated T lymphocytes and monocytes were performed for each blood draw. Dietary grape powder reduced the plasma concentrations of large LDL-cholesterol and large LDL particles compared with the placebo powder (P< 0·05). The concentrations of interferon-γ, TNF-α, IL-4 and IL-10 were measured in supernatants from peripheral blood mononuclear cells (PBMC) activated with anti-CD3/CD28 antibodies and those of TNF-α, IL-1β, IL-6 and IL-8 were measured in supernatants from PBMC activated with lipopolysaccharide (LPS). No difference in the production of T-cell cytokines was observed between the two intervention groups. The production of IL-1β and IL-6 was increased in supernatants from LPS-activated PBMC in the grape powder group compared with the placebo powder group (P< 0·05). These data suggest that dietary grapes may decrease atherogenic lipid fractions in obese individuals and increase the sensitivity of monocytes in a population at a greater risk of developing infections.

Cardiovascular Disease Among Alaska Native Peoples

Although Alaska Native peoples were thought to be protected from cardiovascular disease (CVD), data now show that this is not the case, despite traditional lifestyles and high omega-3 fatty acid intake. In this article, the current understanding of CVD and its risk factors among Alaska Native peoples, particularly among the Yupik and Inupiat populations, will be discussed, using data from three major studies funded by the National Institutes of Health: Genetics of Coronary Artery Disease among Alaska Natives (GOCADAN), Center for Native Health Research (CANHR), and Education and Research Towards Health (EARTH). Data from these epidemiologic studies have focused concern on CVD and its risk factors among Alaska Native peoples. This review will summarize the findings of these three principal studies and will suggest future directions for research and clinical practice.

Clinical factors associated with carotid plaque and intima-medial thickness in HIV-infected patients

PURPOSE

HIV-infected patients are at increased risk for cardiovascular disease, which may be mediated in part by inflammation. This study aimed to evaluate the risk factors of carotid plaque, and clinical factors associated with carotid atherosclerosis measured by carotid intima-medial thickness (cIMT) in HIV patients.

MATERIALS AND METHODS

Clinical and cardiometabolic factors as well as cIMT were prospectively measured in 145 HIV-infected participants who had received combined antiretroviral therapy for ≥6 months. The mean value of the bilateral average cIMT level was used as Mean-IMT in the analysis, and the greatest value among the measured cIMT levels was used as Max-IMT.

RESULTS

Among 145 patients, 34 (23.4%) had carotid plaque. Multivariate logistic regression analysis revealed three independent risk factors of carotid plaque: old age [odds ratio (OR) 6.16, 95% confidence interval (CI) 1.09-34.88; p=0.040], hypertension (OR 12.62, 95% CI 1.72-92.49; p=0.013) and higher low-density lipoprotein cholesterol (LDL-C) (OR 1.08, 95% CI 1.01-1.16; p=0.039). Levels of estimated glomerular filtration rate were inversely associated with Mean-IMT (r=-0.379, p<0.001) and Max-IMT (r=-0.389, p<0.001). Stepwise multivariate regression analyses revealed that age, total cholesterol and fasting glucose were positively correlated with cIMT, independent of other risk factors.

CONCLUSION

The presence of hypertension, old age and a higher level of LDL-C were independent risk factors of carotid plaque among HIV-infected subjects.

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.

Lipoprotein subfractions and dietary intake of n-3 fatty acid: the Genetics of Coronary Artery Disease in Alaska Natives study

BACKGROUND

Few studies have compared lipoprotein composition with dietary intake.

OBJECTIVE

The lipoprotein subfraction profile was evaluated in relation to diet in Alaska Eskimos at high cardiovascular risk but with a low frequency of hyperlipidemia and high intake of n-3 (omega-3) fatty acids.

DESIGN

A population-based sample (n = 1214) from the Norton Sound Region of Alaska underwent a physical examination and blood sampling. Analyses were from 977 individuals who did not have diabetes or use lipid-lowering medications and had complete dietary information (food-frequency questionnaire) and a lipoprotein subfraction profile (nuclear magnetic resonance spectroscopy).

RESULTS

After adjustment for age, BMI, total energy intake, and percentage of energy from fat, the intake of n-3 fatty acids was significantly associated with fewer large VLDLs (P = 0.022 in women, P = 0.064 in men), a smaller VLDL size (P = 0.018 and P = 0.036), more large HDLs (P = 0.179 and P = 0.021), and a larger HDL size (P = 0.004 and P = 0.001). After adjustment for carbohydrate and sugar intakes, large VLDLs (P = 0.042 and 0.018) and VLDL size (P = 0.011 and 0.025) remained negatively associated with n-3 fatty acid intake in women and men, and large HDLs (P = 0.067 and 0.005) and HDL size (P = 0.001 in both) remained positively associated with n-3 fatty acid intake in women and men. In addition, large LDLs (P = 0.040 and P = 0.025) were positively associated in both sexes, and LDL size (P = 0.006) showed a positive association in women. There were no significant relations with total LDL particles in either model.

CONCLUSIONS

Dietary n-3 fatty acids, independent of the reciprocal changes in carbohydrate and sugar intakes, are associated with an overall favorable lipoprotein profile in terms of cardiovascular risk. Because there are no relations with total LDL particles, the benefit may be related to cardiovascular processes other than atherosclerosis.

Low-density lipoprotein particle number predicts coronary artery calcification in asymptomatic adults at intermediate risk of cardiovascular disease

BACKGROUND

Clinicians require more discriminating measures of cardiovascular risk than those currently used in most clinical settings. A promising avenue of research concerns the relationship of low-density lipoprotein (LDL) subfractions to subclinical atherosclerosis.

OBJECTIVE

To assess cross-sectional associations between subfractions of LDL cholesterol and coronary artery calcification (CAC).

METHODS

The study sample comprised 284 asymptomatic clinic patients who were at intermediate risk of cardiovascular disease, aged 40-69 years, who were not taking a statin or niacin. Lipoprotein subclass measures were obtained by the use of proton nuclear magnetic resonance spectroscopy. CAC was assessed with computed tomography angiography (CTA). The analyses modeled the presence or absence of CAC.

RESULTS

Total LDL particle number (LDL-P) had a stronger association with CAC than the traditional lipoprotein measures. Patients in the highest tercile of total LDL-P (1935-3560 nmol/L) were 3.7 times more likely to exhibit coronary artery calcification as those in the lowest tercile (620-1530 nmol/L). The independent effects of small LDL-P remained significant after adjustment for LDL-cholesterol, high-density lipoprotein (HDL), triglycerides, non-HDL, and large LDL-P. HDL and non-HDL were not significant, independent predictors of CAC.

CONCLUSION

Small LDL-P was a strong, independent predictor of the presence of CAC. Large prospective studies are needed to examine the effect of LDL particle number and size on coronary artery calcification.

Lipoprotein subfractions and cardiovascular disease risk

PURPOSE OF REVIEW

Subfractions of LDL and HDL defined by differences in particle size and density have been associated to varying degrees with risk of cardiovascular disease (CVD). Assessment of these relationships has been clouded by lack of standardization among the various analytic methodologies as well as the strong correlations of the subfractions with each other and with standard lipid and lipoprotein risk markers. This review summarizes the properties of the major LDL and HDL particle subclasses, and recent evidence linking their measurement with risk of atherosclerosis and CVD.

RECENT FINDINGS

Several recent studies have shown independent relationships of levels of LDL and HDL-size subclasses to risk of both coronary artery and cerebrovascular disease. However, the two largest studies, employing nuclear magnetic resonance and ion mobility, respectively, did not find evidence that these measurements improved risk assessment compared with standard lipoprotein assays. In the latter study, principal component analysis was used to group multiple subfraction measurements into three distinct and statistically independent clusters that were related both to cardiovascular outcomes and to genotypes that may reflect underlying metabolic determinants.

SUMMARY

Although there is as yet inconclusive evidence as to the extent to which LDL and HDL subfraction measurements improve clinical assessment of CVD risk beyond standard lipid risk markers, recent studies suggest that more refined analyses of lipoprotein subspecies may lead to further improvements in CVD risk evaluation and particularly in identification of appropriate targets for therapeutic intervention in individual patients.