HDL (High-Density Lipoprotein) Subspecies, Prevalent Covert Brain Infarcts, and Incident Overt Ischemic Stroke: Cardiovascular Health Study

BACKGROUND AND PURPOSE

Whether HDL (high-density lipoprotein) is associated with risk of vascular brain injury is unclear. HDL is comprised of many apo (apolipoprotein) species, creating distinct subtypes of HDL.

METHODS

We utilized sandwich ELISA to determine HDL subspecies from plasma collected in 1998/1999 from 2001 CHS (Cardiovascular Health Study) participants (mean age, 80 years).

RESULTS

In cross-sectional analyses, participants with higher apoA1 in plasma and lower apoE in HDL were less likely to have prevalent covert magnetic resonance imaging-defined infarcts: odds ratio for apoA1 Q4 versus Q1, 0.68 (95% CI, 0.50-0.93), and odds ratio for apoE Q4 versus Q1, 1.36 (95% CI, 1.01-1.84). Similarly, apoA1 in the subspecies of HDL that lacked apoC3, apoJ, or apoE was inversely related to covert infarcts, and apoE in the subspecies of HDL that lacked apoC3 or apoJ was directly related to covert infarcts in prospective analyses. In contrast, the concentrations of apoA1 and apoE in the complementary subspecies of HDL that contained these apos were unrelated to covert infarcts. Patterns of associations between incident overt ischemic stroke and apoA1, apoE, and apoA1 and apoE in subspecies of HDL were similar to those observed for covert infarcts but less pronounced.

CONCLUSIONS

This study highlights HDL subspecies defined by apo content as relevant biomarkers of covert and overt vascular brain injury.

Sex-dependent associations of maternal androgen levels with offspring BMI and weight trajectory from birth to early childhood

CONTEXT

In preclinical studies, high androgen levels during pregnancy are associated with low birth weight and rapid postnatal weight gain in the offspring. However, human data linking prenatal androgens with birth weight and early life weight gain in the offspring are scarce.

DESIGN

We evaluated 516 mother-child pairs enrolled in the New England birth cohorts of the Collaborative Perinatal Project (1959-1966). We assayed androgen bioactivity in maternal sera during third-trimester using a receptor-mediated luciferase expression bioassay. Age and sex-specific BMI Z-scores (BMIz), defined using established standards, were assessed at birth, 4 months, 1 year, 4 years, and 7 years. We used linear mixed models to evaluate the relation of maternal androgens with childhood BMIz overall and by sex. We examined the association of maternal androgens with fetal growth restriction. The association of weight trajectories with maternal androgens was examined using multinomial logistic regression.

RESULTS

Higher maternal androgen levels associated with lower BMIz at birth (β = - 0.39, 95% CI: - 0.73, - 0.06); this relation was sex-dependent, such that maternal androgens significantly associated with BMIz at birth in girls alone (β = - 0.72, 95% CI: - 1.40, - 0.04). The relation of maternal androgens with fetal growth restriction revealed dose threshold effects that differed by sex. There was no significant association between maternal androgens and weight trajectory overall. However, we found a significant sex interaction (p = 0.01); higher maternal androgen levels associated with accelerated catch-up growth in boys (aOR = 2.14, 95% CI: 1.14, 4.03).

CONCLUSION

Our findings provide evidence that maternal androgens may have differential effects on the programming of intrauterine growth and postnatal weight gain depending on fetal sex.

Apolipoprotein C-III and its defined lipoprotein subspecies in relation to incident diabetes: the Multi-Ethnic Study of Atherosclerosis

AIMS/HYPOTHESIS

Apolipoprotein C-III (apoC-III) is a small proinflammatory protein that may play a key role in diabetes pathophysiology. However, prior observational studies have been limited to predominantly white populations, and the biological links between apoC-III and diabetes, particularly the role of apoC-III on specific lipoprotein particles, are not yet well understood. We therefore investigated associations of total apoC-III and apoC-III-defined lipoprotein subspecies with incident diabetes and glucose metabolism measures in a multi-ethnic cohort.

METHODS

For the current analyses, baseline (2000-2002) plasma total apoC-III and apolipoprotein A-I concentrations of HDL containing or lacking apoC-III were newly measured via sandwich ELISA in 4579 participants from the Multi-Ethnic Study of Atherosclerosis. Multivariable Cox regression was used to examine associations of apolipoproteins with incident diabetes until early 2012 (567 cases), and linear mixed models were used to estimate associations with longitudinally assessed continuous measures of glucose metabolism. Similar exploratory analyses of plasma apolipoprotein B concentrations of LDL and VLDL containing or lacking apoC-III were performed in a subset of participants (LDL, n = 1545; VLDL, n = 1526).

RESULTS

In the overall population, elevated total apoC-III concentrations were associated with a higher rate of diabetes (top vs bottom quintile, HR 1.88; 95% CI 1.42, 2.47; p_trend = 0.0002). ApoC-III-defined HDL subspecies displayed opposing associations with incidence of diabetes (p for heterogeneity = 0.02). While HDL lacking apoC-III was inversely associated with incidence of diabetes (top vs bottom quintile, HR 0.66; 95% CI 0.46, 0.93; p_trend = 0.002), HDL containing apoC-III was not associated (HR 1.11; 95% CI 0.78, 1.58; p_trend = 0.61). Similarly, only HDL lacking apoC-III was beneficially associated with plasma glucose (p_trend = 0.003), HbA_1c (p_trend = 0.04) and insulin sensitivity (p_trend < 0.0001), and higher HDL containing apoC-III was associated with lower insulin sensitivity (p_trend = 0.04). Neither of the apoC-III-defined LDL subspecies was associated with incident diabetes, while VLDL was more strongly associated with the incidence of diabetes when it lacked apoC-III. Further adjustment for plasma triacylglycerols as a potential intermediate attenuated the associations of total apoC-III and apoC-III-defined lipoprotein subspecies. No statistically significant differences were observed across racial/ethnic groups.

CONCLUSIONS/INTERPRETATION

Our findings in a multi-ethnic population support the involvement of apoC-III in the development of diabetes, potentially through its association with circulating triacylglycerols. The presence of apoC-III on HDL also diminished the protective association of HDL with incident diabetes. Further investigation of apoC-III and apoC-III-defined HDL subspecies may inform the development of novel diabetes treatment and prevention strategies.

High-Density Lipoprotein Subspecies Defined by Apolipoprotein C-III and Subclinical Atherosclerosis Measures: MESA (The Multi-Ethnic Study of Atherosclerosis)

Background

Apolipoprotein C‐III (apoC‐III), a small proinflammatory protein present on 6% to 7% of high‐density lipoprotein (HDL) particles, defines a subspecies of HDL adversely associated with coronary heart disease in primarily white cohorts. In a multi‐ethnic population free of clinical cardiovascular disease, we evaluated the relationship between apoC‐III–defined HDL subspecies and subclinical markers of atherosclerotic pathology.

Methods and Results

We investigated cross‐sectional associations between apolipoprotein A‐I concentrations of apoC‐III–defined HDL subspecies, measured via ELISA and imaging measures of subclinical atherosclerosis, among 4659 participants in the MESA (The Multi‐Ethnic Study of Atherosclerosis) at baseline (2000–2002). HDL particles containing and lacking apoC‐III were divergently associated with coronary artery calcification in women (P‐heterogeneity=0.002) but not in men (P‐heterogeneity=0.31) and with carotid plaque score (P‐heterogeneity=0.02) and intima‐media thickness (P‐heterogeneity=0.06) in the overall study population. HDL lacking apoC‐III was inversely associated with all outcome measures (coronary artery calcification, women: odds ratio per SD=0.81 [95% confidence interval [CI], 0.73–0.90]; carotid plaque, overall: odds ratio per SD=0.92 [95% CI, 0.84–1.00]; intima‐media thickness, overall: mean difference per SD=−14.0 µm [95% CI, −21.1 to −6.7 μm]), whereas HDL containing apoC‐III was positively associated (coronary artery calcification, women: odds ratio=1.10 [95% CI, 0.99–1.22]; plaque, overall: odds ratio=1.10 [95% CI, 1.01–1.19]) or unassociated. Neither total HDL nor HDL subspecies was associated with changes in subclinical atherosclerosis measures up to 10 years later.

Conclusions

The presence of apoC‐III defined a subspecies of HDL not inversely associated with baseline measures of subclinical atherosclerosis, supporting a role of apoC‐III in the pathophysiology of cardiovascular disease.

High density lipoprotein with apolipoprotein C-III is associated with carotid intima-media thickness among generally healthy individuals

BACKGROUND AND AIMS

About 6-7% of high density lipoprotein (HDL) has a protein called apolipoprotein (apo) C-III that regulates lipoprotein metabolism and can provoke an inflammatory response. HDL without apoC-III is inversely associated with coronary heart disease (CHD), whereas HDL with apoC-III is directly associated with CHD. We investigated how the presence of apoC-III affects the association between HDL and early stages of atherosclerosis measured as carotid intima-media thickness (cIMT).

METHODS

We examined the cross-sectional associations between the apoA-I concentrations of HDL subspecies with and without apoC-III and cIMT measured by high resolution B-mode carotid ultrasonography among 847 participants from the European multi-center Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study.

RESULTS

HDL with and without apoC-III demonstrated significantly opposite associations with both cIMT indexes (p-heterogeneity of associations comparing the two subspecies was 0.002 for cIMT at common carotid artery (cIMT at CCA) and 0.006 for the maximum cIMT in any carotid segment (cIMT max)). Compared to the lowest quintile, the highest quintile of apoA-I in HDL without apoC-III was associated with 3.7% lower cIMT at CCA (p-trend = 0.01) or 7.3% lower cIMT max (p-trend = 0.003), while the highest quintile of apoA-I in HDL with apoC-III was associated with 4.4% higher cIMT at CCA (p-trend = 0.001) or 7.9% higher cIMT max (p-trend = 0.002). Total apoA-I as well as total HDL cholesterol was not associated with cIMT whereas higher levels of total apoC-III and apoC-III contained in HDL were significantly associated with higher cIMT (p-trend<0.01).

CONCLUSIONS

HDL apoC-III is a promising target for atherosclerosis prevention and treatment.

High-Density Lipoprotein Subspecies Defined by Presence of Apolipoprotein C-III and Incident Coronary Heart Disease in Four Cohorts

BACKGROUND

The causal role of high-density lipoprotein (HDL) cholesterol in cardioprotection has been questioned by genetic and randomized studies. Novel measures that relate to HDL function may contribute new information to the prediction of cardiovascular risk. Apolipoprotein C-III (apoC-III) is a key regulator of lipoprotein metabolism. We investigated whether subspecies of HDL defined by apoC-III are associated with coronary heart disease (CHD).

METHODS

We used immunoaffinity chromatography to measure the apoA-I concentrations of HDL that contains and lacks apoC-III in 2 prospective studies of adults free of CHD. In MESA (Multi-Ethnic Study of Atherosclerosis), 5657 participants (52% women, 52-72 years of age) were followed for risk of CHD from 2000 to 2002 through 2013. In a case-cohort study nested within the DCH study (Danish Diet, Cancer, and Health), 3642 participants (47% women, 51-64 years of age) were followed from 1994 to 1997 through 2010. Subsequently, we conducted a meta-analysis that combined these results with the previously published findings from 2 cohort studies that used similar laboratory methodology to measure lipoproteins, totaling 2997 incident cases.

RESULTS

ApoC-III was found on 6% to 8% of apoA-I. The 2 HDL subspecies showed opposing associations, with risk of CHD in each of the individual cohorts and in the meta-analysis (P heterogeneity between the 2 subspecies <0.01). HDL that contains apoC-III was associated with a higher risk of CHD (pooled relative risk per standard deviation, 1.09; 95% confidence interval, 1.01-1.18), whereas HDL that lacks apoC-III was associated with lower risk (relative risk, 0.76; 95% confidence interval, 0.70-0.83). The relative risk for HDL lacking apoC-III was even more negative than the relative risk for total HDL (relative risk, 0.80; 95% confidence interval, 0.74-0.87).

CONCLUSIONS

Our findings from 4 prospective studies support the hypothesis that apoC-III may mark a subfraction of HDL that is associated with higher risk of CHD. New measures reflecting HDL structure and function may provide novel insights for cardiovascular risk that extend beyond traditional plasma HDL cholesterol concentrations.

Apolipoprotein C-III and High-Density Lipoprotein Subspecies Defined by Apolipoprotein C-III in Relation to Diabetes Risk

Apolipoprotein C-III (apoC-III) is a potentially novel biomarker that may play an important role in the pathogenesis of diabetes, particularly when present on the surface of high-density lipoprotein (HDL). In a case-cohort study carried out among 434 incident diabetes cases occurring before 2007 and 3,101 noncases in the Danish Diet, Cancer, and Health Study, we examined associations of baseline (1993-1997) plasma concentrations of apoC-III and subspecies of HDL defined by the presence or absence of apoC-III with risk of diabetes using Cox regression. ApoC-III was strongly associated with risk of diabetes (for top quintile vs. bottom quintile, hazard ratio (HR) = 3.43, 95% confidence interval (CI): 1.75, 6.70; P-trend < 0.001). The cholesterol concentration of HDL (HDL cholesterol (HDL-C)) without apoC-III was inversely associated with risk of diabetes (HR = 0.48, 95% CI: 0.27, 0.85; P-trend = 0.002), more so than total HDL-C (HR = 0.60, 95% CI: 0.35, 1.03; P-trend = 0.04), whereas HDL-C with apoC-III was not associated (HR = 1.05, 95% CI: 0.50, 2.21; P-trend = 0.44) (for HDL-C with apoC-III vs. HDL-C without apoC-III, P-heterogeneity = 0.002). ApoC-III itself is a strong risk marker for diabetes, and its presence on HDL may impair the antidiabetogenic properties of HDL. ApoC-III has potential to be a therapeutic target for the prevention of diabetes.

Fetuin-A and Risk of Diabetes Independent of Liver Fat Content: The Multi-Ethnic Study of Atherosclerosis

Fetuin-A is a hepatic secretory protein and a novel risk factor for diabetes. However, it remains unclear whether the association between high levels of fetuin-A and diabetes can be attributed to nonalcoholic fatty liver disease. We conducted a case-cohort study among 1,957 subcohort members and 455 incident diabetes cases in the Multi-Ethnic Study of Atherosclerosis, a multicenter US study of Caucasian, African-American, Hispanic, and Chinese-American adults aged 45-84 years. Serum fetuin-A and computed tomography-determined liver fat content were measured from samples collected at baseline (2000-2002). In multivariable Cox proportional hazards models with follow-up through 2012, a higher fetuin-A level was associated with a higher risk of diabetes, with a stronger association among women (for top quartile vs. bottom, hazard ratio (HR) = 3.36, 95% confidence interval (CI): 2.08, 5.44) than among men (HR = 1.47, 95% CI: 0.93, 2.35) (P-heterogeneity = 0.001). Adjustment for liver fat content attenuated these associations slightly (women: HR = 2.61, 95% CI: 1.59, 4.26; men: HR = 1.32, 95% CI: 0.84, 2.08). In this study, we observed a particularly strong association of fetuin-A with diabetes risk in women that could not be explained by liver fat.

Breast cancer risk by extent and type of atypical hyperplasia: An update from the Nurses' Health Studies

BACKGROUND

Women with atypical hyperplasia (AH) on a benign breast biopsy specimen are at increased risk for the development of breast cancer. However, the relation between the type and extent of AH (atypical ductal hyperplasia [ADH] vs atypical lobular hyperplasia [ALH]) and the magnitude of the breast cancer risk is not well defined.

METHODS

A nested case-control study of benign breast disease and breast cancer risk was conducted. Women with breast cancer and prior benign breast biopsy findings (488 cases) were matched to women with prior benign breast biopsy findings who were free from breast cancer (1907 controls). Benign breast biopsy slides were reviewed and categorized as nonproliferative, proliferative without atypia, or AH (ADH or ALH). The number of foci of AH was also recorded.

RESULTS

Among women with ADH, the interrelation between the extent of atypia and breast cancer risk was not significant (odds ratio [OR] for 1 or 2 foci, 3.5; 95% confidence interval [CI], 2.2-5.6; OR for ≥3 foci, 2.7; 95% CI, 1.4-5.1; P = .41). Similarly, although the risk with ALH was higher for those with ≥3 foci than for those with <3 foci, the difference was not statistically significant (OR for 1 or 2 foci, 5.2; 95% CI, 2.7-10.0; OR for ≥3 foci, 8.0; 95% CI, 4.5-14.2; P = .19).

CONCLUSIONS

This analysis demonstrates that the extent of ADH or ALH does not significantly contribute to breast cancer risk. The lack of a significant dose-response relation between the extent and type of atypia and breast cancer risk suggests that it would be premature to use the extent of atypia to influence management decisions for women with ADH or ALH.

New and emerging biomarkers in cardiovascular disease

Cardiovascular disease (CVD) is the most common cause of death and disability worldwide. Therefore, great importance has been placed on the discovery of novel risk factors and metabolic pathways relevant in the prevention and management of CVD. Such research is ongoing and may continue to lead to better risk stratification of individuals and/or the development of new intervention targets and treatment options. This review highlights emerging biomarkers related to lipid metabolism, glycemia, inflammation, and cardiac damage, some of which show promising associations with CVD risk and provide further understanding of the underlying pathophysiology. However, their measurement methodology and assays will require validation and standardization, and it will take time to accumulate evidence of their role in CVD in various population settings in order to fully assess their clinical utility. Several of the novel biomarkers represent intriguing, potentially game-changing targets for therapy.

Plasma matrix metalloproteinase 2 levels and breast cancer risk

Matrix metalloproteinase 2 (MMP2) is an enzyme with important functions in breast cancer invasion and metastasis. However, it is unclear whether circulating MMP2 levels may predict breast cancer risk. We conducted a prospective nested case-control analysis in the Nurses' Health Study among 1136 cases who were diagnosed with invasive breast cancer between 1992 and 2004 and 1136 matched controls. All participants provided blood samples in 1989-1990, and a subset (170 cases, 170 controls) contributed an additional sample in 2000-2002. Pre-diagnostic plasma MMP2 levels were measured via immunoassay, and conditional logistic regression was performed to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs), adjusted for breast cancer risk factors. No association was observed between plasma MMP2 levels and risk of total invasive breast cancer (top vs. bottom quartile, OR=1.0; 95% CI: 0.7, 1.2; p-trend=0.89). Findings did not vary significantly by time since blood draw, body mass index, postmenopausal hormone use, or menopausal status at either blood draw or breast cancer diagnosis. MMP2 was associated with a greater risk of nodal metastases at diagnosis (top vs. bottom quartile, OR=1.5; 95% CI: 1.0, 2.2; p-heterogeneity, any vs. no lymph nodes=0.002), but no significant associations were observed with other tumor characteristics or with recurrent or fatal cancers. Plasma MMP2 levels do not appear to be predictive of total invasive breast cancer risk, although associations with aggressive disease warrant further study.

Plasma matrix metalloproteinase 1, 3, and 7 levels and breast cancer risk in the Nurses' Health study

PURPOSE

Matrix metalloproteinases (MMPs), in particular MMP1, 3, and 7, are believed to be critical to breast cancer invasion and metastasis and also may have important functions earlier in breast carcinogenesis. However, the relationship between circulating levels of MMP1, 3, and 7 and breast cancer risk is uncertain.

METHODS

We examined associations between plasma MMP1, 3, and 7 and breast cancer risk in a prospective case-control study nested within the Nurses' Health Study. Blood samples were collected from 801 cases who developed breast cancer between 1992 and 2000 and 801 matched controls, and MMP levels were measured via immunofluorescence assay.

RESULTS

No overall association was observed between any of these MMPs and breast cancer risk [top vs. bottom quintile; MMP1: odds ratio (OR) 0.9; 95 % confidence interval (CI) 0.7, 1.3; p-trend = 0.51; MMP3: OR 1.1; 95 % CI 0.8, 1.5; p-trend = 0.88; MMP7: OR = 1.2; 95 % CI 0.8, 1.7; p-trend = 0.18]. Further, findings did not significantly vary by time since blood draw, body mass index, or postmenopausal hormone use, or by breast cancer subtypes.

CONCLUSIONS

Circulating MMP1, 3, and 7 levels do not appear to be predictive of overall breast cancer risk.

Radial scars and subsequent breast cancer risk: results from the Nurses' Health Studies

Radial scars (RS) are benign proliferative lesions associated with an increased risk of subsequent breast cancer. However, it remains unclear whether RS are an independent risk factor for breast cancer or whether their association with breast cancer is due to their common occurrence with other proliferative lesions known to increase breast cancer risk. We performed an updated analysis of the association between RS and subsequent breast cancer risk in a nested case-control study among 460 cases and 1,792 controls with benign breast disease (BBD) in the Nurses' Health Studies. Logistic regression was used to estimate associations between RS in BBD biopsy specimens and breast cancer risk, adjusted for matching factors and breast cancer risk factors, including histologic category of concurrent BBD. In multivariable models prior to adjustment for histologic category of BBD, RS were associated with a twofold increased risk of breast cancer (odds ratio (OR) = 2.0; 95 % confidence interval (95 % CI) 1.4, 2.8). This association was attenuated but still significant after adjustment for BBD histologic category (OR = 1.6; 95 % CI 1.1, 2.3). In models adjusted for BBD histologic category and other covariates, risk appeared greater among women with multiple RS (1 RS, OR = 1.5; 95 % CI 0.9, 2.3; ≥2 RS, OR = 2.7; 95 % CI 1.5, 5.0; p-heterogeneity = 0.12). There were also suggestions of a greater risk associated with RS among women age ≥50 years at biopsy (p-heterogeneity = 0.07) and for estrogen receptor-negative/progesterone receptor-negative tumors compared with other hormone receptor subtypes (p-heterogeneity = 0.19). RS appear to be an independent histologic risk factor for breast cancer. Larger studies are needed to further evaluate whether risk is increased when multiple RS are present and whether associations vary by age at biopsy or by hormone receptor status of the breast tumor.