Food Intake Suppresses ApoB Secretion and Fractional Catabolic Rates in Humans.

BACKGROUND: Humans spend much of the day in the postprandial state. However, most research and clinical guidelines on plasma lipids pertain to blood drawn after a 12-hour fast. We aimed to study the metabolic differences of apoB lipoproteins between the fasting and postprandial states. METHODS: We investigated plasma apoB metabolism using stable isotope tracers in 12 adult volunteers under fasting and continuous postprandial conditions in a randomized crossover study. We determined the metabolism of apoB in multiple lipoprotein subfractions, including light and dense VLDLs (very-low-density lipoproteins), IDLs (intermediate-density lipoproteins), and light and dense LDLs (low-density lipoproteins) that do or do not contain apoE or apoC3. RESULTS: A major feature of the postprandial state is 50% lower secretion rate of triglyceride-rich lipoproteins and concurrent slowdown of their catabolism in circulation, as shown by 34% to 55% lower rate constants for the metabolic pathways of conversion by lipolysis from larger to smaller lipoproteins and direct clearance of lipoproteins from the circulation. In addition, the secretion pattern of apoB lipoprotein phenotypes was shifted from particles containing apoE and apoC3 in the fasting state to those without either protein in the postprandial state. CONCLUSIONS: Overall, during the fasting state, hepatic apoB lipoprotein metabolism is activated, characterized by increased production, transport, and clearance. After food intake, endogenous apoB lipoprotein metabolism is globally reduced as appropriate to balance dietary input to maintain the supply of energy to peripheral tissues.

MTNR1B genotype and effects of carbohydrate quantity and dietary glycaemic index on glycaemic response to an oral glucose load: the OmniCarb trial.

AIMS/HYPOTHESIS: A type 2 diabetes-risk-increasing variant, MTNR1B (melatonin receptor 1B) rs10830963, regulates the circadian function and may influence the variability in metabolic responses to dietary carbohydrates. We investigated whether the effects of carbohydrate quantity and dietary glycaemic index (GI) on glycaemic response during OGTTs varied by the risk G allele of MTNR1B-rs10830963. METHODS: This study included participants (n=150) of a randomised crossover-controlled feeding trial of four diets with high/low GI levels and high/low carbohydrate content for 5 weeks. The MTNR1B-rs10830963 (C/G) variant was genotyped. Glucose response during 2 h OGTT was measured at baseline and the end of each diet intervention. RESULTS: Among the four study diets, carrying the risk G allele (CG/GG vs CC genotype) of MTNR1B-rs10830963 was associated with the largest AUC of glucose during 2 h OGTT after consuming a high-carbohydrate/high-GI diet (ß 134.32 [SE 45.69] mmol/l × min; p=0.004). The risk G-allele carriers showed greater increment of glucose during 0-60 min (ß 1.26 [0.47] mmol/l; p=0.008) or 0-90 min (ß 1.10 [0.50] mmol/l; p=0.028) after the high-carbohydrate/high-GI diet intervention, but not after consuming the other three diets. At high carbohydrate content, reducing GI levels decreased 60 min post-OGTT glucose (mean -0.67 [95% CI: -1.18, -0.17] mmol/l) and the increment of glucose during 0-60 min (mean -1.00 [95% CI: -1.67, -0.33] mmol/l) and 0-90 min, particularly in the risk G-allele carriers (pinteraction <0.05 for all). CONCLUSIONS/INTERPRETATION: Our study shows that carrying the risk G allele of MTNR1B-rs10830963 is associated with greater glycaemic responses after consuming a diet with high carbohydrates and high GI levels. Reducing GI in a high-carbohydrate diet may decrease post-OGTT glucose concentrations among the risk G-allele carriers.

Dietary Macronutrients and Circulating Nonesterified Fatty Acids: A Secondary Analysis of the OMNI Heart Crossover Trial.

BACKGROUND: Nonesterified fatty acids (NEFAs) play key roles in the pathophysiology of diabetes and cardiovascular disease. OBJECTIVES: We sought to determine whether macronutrient content differences affect NEFA concentrations in a randomized crossover trial. METHODS: Total NEFAs were measured from postintervention specimens of participants in the OMNI Heart trial (Optimal Macronutrient Intake Trial to Prevent Heart Disease). OMNI Heart compared 3 healthful diets to evaluate their effect on systolic blood pressure and serum LDL cholesterol: carbohydrate-rich diet (58% carbohydrate); protein-rich diet (25% protein), about half from plant sources; and a diet rich in unsaturated fatty acids (21% unsaturated fat), predominantly monounsaturated. The trial included 164 participants who consumed the 3 diets, each for 6 wk. Data were analyzed from the 156 participants with unthawed serum available from the week 6 visit for all diet periods. We used ANCOVA and generalized estimating equations (GEEs) to compare serum NEFA concentrations across the 3 diet periods. RESULTS: The mean ± SD age of study participants was 52.9 ± 10.6 y and mean BMI was 30.3 ± 6.1 kg/m2. Fifty-five percent of participants were women and 55% were African American. Comparisons of adjusted mean serum NEFA concentrations after each diet intervention identified no statistically significant differences (58% carbohydrate: 0.144 ± 0.083 mEq/L; 25% protein: 0.143 ± 0.076 mEq/L; 21% unsaturated fat: 0.143 ± 0.084 mEq/L; ANCOVA, P = 0.99). Likewise, we observed no significant serum NEFA concentration difference by diet in adjusted GEE models. In adjusted models, serum NEFA concentrations were positively associated, as anticipated, with female sex and higher BMI. CONCLUSIONS: In this randomized crossover trial, we observed nearly identical serum NEFA concentrations after each of 3 healthful diets, regardless of macronutrient content.

Pharmacological Inhibition of CETP (Cholesteryl Ester Transfer Protein) Increases HDL (High-Density Lipoprotein) That Contains ApoC3 and Other HDL Subspecies Associated With Higher Risk of Coronary Heart Disease.

OBJECTIVE: Plasma total HDL (high-density lipoprotein) is a heterogeneous mix of many protein-based subspecies whose functions and associations with coronary heart disease vary. We hypothesize that increasing HDL by CETP (cholesteryl ester transfer protein) inhibition failed to reduce cardiovascular disease risk, in part, because it increased dysfunctional subspecies associated with higher risk such as HDL that contains apoC3. Approach and Results: We studied participants in 2 randomized, double-blind, placebo-controlled trials of a CETP inhibitor on a background of atorvastatin treatment: ACCENTUATE (The Addition of Evacetrapib to Atorvastatin Compared to Placebo, High Intensity Atorvastatin, and Atorvastatin With Ezetimibe to Evaluate LDL-C Lowering in Patients With Primary Hyperlipidemia; 130 mg evacetrapib; n=126) and ILLUMINATE (Phase 3 Multi Center, Double Blind, Randomized, Parallel Group Evaluation of the Fixed Combination Torcetrapib/Atorvastatin, Administered Orally, Once Daily [Qd], Compared With Atorvastatin Alone, on the Occurrence of Major Cardiovascular Events in Subjects With Coronary Heart Disease or Risk Equivalents; 60 mg torcetrapib; n=80). We measured the concentration of apoA1 in total plasma and 17 protein-based HDL subspecies at baseline and 3 months. Both CETP inhibitors increased apoA1 in HDL that contains apoC3 the most of all HDL subspecies (median placebo-adjusted percent increase: evacetrapib 99% and torcetrapib 50%). They also increased apoA1 in other HDL subspecies associated with higher coronary heart disease risk such as those involved in inflammation (α-2-macroglobulin and complement C3) or hemostasis (plasminogen), and in HDL that contains both apoE and apoC3, a complex subspecies associated with higher coronary heart disease risk. ApoA1 in HDL that contains apoC1, associated with lower risk, increased 71% and 40%, respectively. Only HDL that contains apoL1 showed no response to either drug. CONCLUSIONS: CETP inhibitors evacetrapib and torcetrapib increase apoA1 in HDL subspecies that contain apoC3 and other HDL subspecies associated with higher risk of coronary heart disease. Subspecies-specific effects shift HDL subspecies concentrations toward a profile associated with higher risk, which may contribute to lack of clinical benefit from raising HDL by pharmaceutical CETP inhibition.

Proteomic Determinants of Variation in Cholesterol Efflux: Observations from the Dallas Heart Study.

High-density lipoproteins (HDLs) are promising targets for predicting and treating atherosclerotic cardiovascular disease (ASCVD), as they mediate removal of excess cholesterol from lipid-laden macrophages that accumulate in the vasculature. This functional property of HDLs, termed cholesterol efflux capacity (CEC), is inversely associated with ASCVD. HDLs are compositionally diverse, associating with >250 different proteins, but their relative contribution to CEC remains poorly understood. Our goal was to identify and define key HDL-associated proteins that modulate CEC in humans. The proteomic signature of plasma HDL was quantified in 36 individuals in the multi-ethnic population-based Dallas Heart Study (DHS) cohort that exhibited persistent extremely high (>=90th%) or extremely low CEC (<=10th%) over 15 years. Levels of apolipoprotein (Apo)A-I associated ApoC-II, ApoC-III, and ApoA-IV were differentially correlated with CEC in high (r = 0.49, 0.41, and -0.21 respectively) and low (r = -0.46, -0.41, and 0.66 respectively) CEC groups (p for heterogeneity (pHet) = 0.03, 0.04, and 0.003 respectively). Further, we observed that levels of ApoA-I with ApoC-III, complement C3 (CO3), ApoE, and plasminogen (PLMG) were inversely associated with CEC in individuals within the low CEC group (r = -0.11 to -0.25 for subspecies with these proteins vs. r = 0.58 to 0.65 for subspecies lacking these proteins; p < 0.05 for heterogeneity). These findings suggest that enrichment of specific proteins on HDLs and, thus, different subspecies of HDLs, differentially modulate the removal of cholesterol from the vasculature.

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

BACKGROUND: 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.

Concentrations of fat-soluble nutrients and blood inflammatory compounds in mother-infant dyads at birth.

BACKGROUND: Perinatal inflammation adversely affects health. Therefore, aims of this IRB-approved study are: (1) compare inflammatory compounds within and between maternal and umbilical cord blood samples at the time of delivery, (2) assess relationships between inflammatory compounds in maternal and cord blood with birth characteristics/outcomes, and (3) assess relationships between blood and placental fat-soluble nutrients with blood levels of individual inflammatory compounds. METHODS: Mother-infant dyads were enrolled (n = 152) for collection of birth data and biological samples of maternal blood, umbilical cord blood, and placental tissue. Nutrient levels included: lutein + zeaxanthin; lycopene; α-, ß-carotene; ß-cryptoxanthin; retinol; α-, γ-, δ-tocopherol. Inflammatory compounds included: tumor necrosis factor-α, superoxide dismutase, interleukins (IL) 1ß, 2, 6, 8, 10. RESULTS: Median inflammatory compound levels were 1.2-2.3 times higher in cord vs. maternal blood, except IL2 (1.3 times lower). Multiple significant correlations existed between maternal vs. infant inflammatory compounds (range of r = 0.22-0.48). While relationships existed with blood nutrient levels, the most significant were identified in placenta where all nutrients (except δ-tocopherol) exhibited relationships with inflammatory compounds. Relationships between anti-inflammatory nutrients and proinflammatory compounds were primarily inverse. CONCLUSION: Inflammation is strongly correlated between mother-infant dyads. Fat-soluble nutrients have relationships with inflammatory compounds, suggesting nutrition is a modifiable factor. IMPACT: Mother and newborn inflammation status are strongly interrelated. Levels of fat-soluble nutrients in blood, but especially placenta, are associated with blood levels of proinflammatory and anti-inflammatory compounds in both mother and newborn infant. As fat-soluble nutrient levels are associated with blood inflammatory compounds, nutrition is a modifiable factor to modulate inflammation and improve perinatal outcomes.

Protein-Defined Subspecies of HDLs (High-Density Lipoproteins) and Differential Risk of Coronary Heart Disease in 4 Prospective Studies.

OBJECTIVE: HDL (high-density lipoprotein) contains functional proteins that define single subspecies, each comprising 1% to 12% of the total HDL. We studied the differential association with coronary heart disease (CHD) of 15 such subspecies. Approach and Results: We measured plasma apoA1 (apolipoprotein A1) concentrations of 15 protein-defined HDL subspecies in 4 US-based prospective studies. Among participants without CVD at baseline, 932 developed CHD during 10 to 25 years. They were matched 1:1 to controls who did not experience CHD. In each cohort, hazard ratios for each subspecies were computed by conditional logistic regression and combined by meta-analysis. Higher levels of HDL subspecies containing alpha-2 macroglobulin, CoC3 (complement C3), HP (haptoglobin), or PLMG (plasminogen) were associated with higher relative risk compared with the HDL counterpart lacking the defining protein (hazard ratio range, 0.96-1.11 per 1 SD increase versus 0.73-0.81, respectively; P for heterogeneity <0.05). In contrast, HDL containing apoC1 or apoE were associated with lower relative risk compared with the counterpart (hazard ratio, 0.74; P=0.002 and 0.77, P=0.001, respectively). CONCLUSIONS: Several subspecies of HDL defined by single proteins that are involved in thrombosis, inflammation, immunity, and lipid metabolism are found in small fractions of total HDL and are associated with higher relative risk of CHD compared with HDL that lacks the defining protein. In contrast, HDL containing apoC1 or apoE are robustly associated with lower risk. The balance between beneficial and harmful subspecies in a person's HDL sample may determine the risk of CHD pertaining to HDL and paths to treatment.

High density lipoprotein and its apolipoprotein-defined subspecies and risk of dementia.

Whether HDL is associated with dementia risk is unclear. In addition to apoA1, other apolipoproteins are found in HDL, creating subspecies of HDL that may have distinct metabolic properties. We measured apoA1, apoC3, and apoJ levels in plasma and apoA1 levels in HDL that contains or lacks apoE, apoJ, or apoC3 using a modified sandwich ELISA in a case-cohort study nested within the Ginkgo Evaluation of Memory Study. We included 995 randomly selected participants and 521 participants who developed dementia during a mean of 5.1 years of follow-up. The level of total apoA1 was not significantly related to dementia risk, regardless of the coexistence of apoC3, apoJ, or apoE. Higher levels of total plasma apoC3 were associated with better cognitive function at baseline (difference in Modified Mini-Mental State Examination scores tertile 3 vs. tertile 1: 0.60; 95% CI: 0.23, 0.98) and a lower dementia risk (adjusted hazard ratio tertile 3 vs. tertile 1: 0.73; 95% CI: 0.55, 0.96). Plasma concentrations of apoA1 in HDL and its apolipoprotein-defined subspecies were not associated with cognitive function at baseline or with the risk of dementia during follow-up. Similar studies in other populations are required to better understand the association between apoC3 and Alzheimer's disease pathology.

Circulating Very-Long-Chain SFA Concentrations Are Inversely Associated with Incident Type 2 Diabetes in US Men and Women.

BACKGROUND: Very-long-chain SFAs (VLCSFAs), such as arachidic acid (20:0), behenic acid (22:0), and lignoceric acid (24:0), have demonstrated inverse associations with cardiometabolic conditions, although more evidence is needed to characterize their relation with risk of type 2 diabetes (T2D). In addition, little is known regarding their potential dietary and lifestyle predictors. OBJECTIVE: We aimed to examine the association of plasma and erythrocyte concentrations of VLCSFAs with incident T2D risk. METHODS: We used existing measurements of fatty acid concentrations in plasma and erythrocytes among 2854 and 2831 participants in the Nurses' Health Study (NHS) and Health Professionals Follow-Up Study (HPFS), respectively. VLCSFAs were measured using GLC, and individual fatty acid concentrations were expressed as a percentage of total fatty acids. Incident T2D cases were identified by self-reports and confirmed by a validated supplementary questionnaire. Cox proportional hazards regression was used to evaluate the association between VLCSFAs and T2D, adjusting for demographic, lifestyle, and dietary variables. RESULTS: During 39,941 person-years of follow-up, we documented 243 cases of T2D. Intakes of peanuts, peanut butter, vegetable fat, dairy fat, and palmitic/stearic (16:0-18:0) fatty acids were significantly, albeit weakly, correlated with plasma and erythrocyte VLCSFA concentrations (|rs| ≤ 0.19). Comparing the highest with the lowest quartiles of plasma concentrations, pooled HRs (95% CIs) were 0.51 (0.35, 0.75) for arachidic acid, 0.43 (0.28, 0.64) for behenic acid, 0.40 (0.27, 0.61) for lignoceric acid, and 0.41 (0.27, 0.61) for the sum of VLCSFAs, after multivariate adjustments for demographic, lifestyle, and dietary factors. For erythrocyte VLCSFAs, only arachidic acid and behenic acid concentrations were inversely associated with T2D risk. CONCLUSIONS: Our findings suggest that, in US men and women, higher plasma concentrations of VLCSFAs are associated with lower risk of T2D. More research is needed to understand the mechanistic pathways underlying these associations.

Associations of Perfluoroalkyl substances with blood lipids and Apolipoproteins in lipoprotein subspecies: the POUNDS-lost study.

BACKGROUND: The associations of perfluoroalkyl substance (PFAS) exposure with blood lipids and lipoproteins are inconsistent, and existing studies did not account for metabolic heterogeneity of lipoprotein subspecies. This study aimed to examine the associations between plasma PFAS concentrations and lipoprotein and apolipoprotein subspecies. METHODS: The study included 326 men and women from the 2-year Prevention of Obesity Using Novel Dietary Strategies (POUNDS) Lost randomized trial. Five PFASs, including perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA), were measured in plasma at baseline. For lipoprotein and apolipoprotein subspecies, total plasma was fractionated first by apolipoprotein (apo) C-III content and then by density. Each subfraction was then measured for apoB, apoC-III, and apoE concentrations, as well as triglyceride and cholesterol contents, both at baseline and at 2 years. RESULTS: For lipids and apolipoproteins in total plasma at baseline, elevated plasma PFAS concentrations were significantly associated with higher apoB and apoC-III concentrations, but not with total cholesterol or triglycerides. After multivariate adjustment of lifestyle factors, lipid-lowering medication use, and dietary intervention groups, PFAS concentrations were primarily associated with lipids or apolipoprotein concentrations in intermediate-to-low density lipoprotein (IDL + LDL) and high-density lipoprotein (HDL) that contain apoC-III. Comparing the highest and lowest tertiles of PFOA, the least-square means (SE) (mg/dl) were 4.16 (0.4) vs 3.47 (0.4) for apoB (P trend = 0.04), 2.03 (0.2) vs 1.66 (0.2) for apoC-III (P trend = 0.04), and 8.4 (0.8) vs 6.8 (0.8) for triglycerides (P trend = 0.03) in IDL + LDL fraction that contains apoC-III. For HDL that contains apoC-III, comparing the highest and lowest tertiles of PFOA, the least-square means (SE) (mg/dl) of apoC-III were 11.9 (0.7) vs 10.4 (0.7) (P trend = 0.01). In addition, elevated PFNA and PFDA concentrations were also significantly associated with higher concentrations of apoE in HDL that contains apoC-III (P trend< 0.01). Similar patterns of associations were demonstrated between baseline PFAS concentrations and lipoprotein subspecies measured at 2 years. Baseline PFAS levels were not associated with changes in lipoprotein subspecies during the intervention. CONCLUSIONS: Our results suggest that plasma PFAS concentrations are primarily associated with blood lipids and apolipoproteins in subspecies of IDL, LDL, and HDL that contain apoC-III, which are associated with elevated cardiovascular risk in epidemiological studies. Future studies of PFAS-associated cardiovascular risk should focus on lipid subfractions.

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; ptrend = 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; ptrend = 0.002), HDL containing apoC-III was not associated (HR 1.11; 95% CI 0.78, 1.58; ptrend = 0.61). Similarly, only HDL lacking apoC-III was beneficially associated with plasma glucose (ptrend = 0.003), HbA1c (ptrend = 0.04) and insulin sensitivity (ptrend < 0.0001), and higher HDL containing apoC-III was associated with lower insulin sensitivity (ptrend = 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 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.

Distinct Proteomic Signatures in 16 HDL (High-Density Lipoprotein) Subspecies.

Objective- HDL (high-density lipoprotein) in plasma is a heterogeneous group of lipoproteins typically containing apo AI as the principal protein. Most HDLs contain additional proteins from a palate of nearly 100 HDL-associated polypeptides. We hypothesized that some of these proteins define distinct and stable apo AI HDL subspecies with unique proteomes that drive function and associations with disease. Approach and Results- We produced 17 plasma pools from 80 normolipidemic human participants (32 men, 48 women; aged 21-66 years). Using immunoaffinity isolation techniques, we isolated apo AI containing species from plasma and then used antibodies to 16 additional HDL protein components to isolate compositional subspecies. We characterized previously described HDL subspecies containing apo AII, apo CIII, and apo E; and 13 novel HDL subspecies defined by presence of apo AIV, apo CI, apo CII, apo J, α-1-antitrypsin, α-2-macroglobulin, plasminogen, fibrinogen, ceruloplasmin, haptoglobin, paraoxonase-1, apo LI, or complement C3. The novel species ranged in abundance from 1% to 18% of total plasma apo AI. Their concentrations were stable over time as demonstrated by intraclass correlations in repeated sampling from the same participants over 3 to 24 months (0.33-0.86; mean 0.62). Some proteomes of the subspecies relative to total HDL were strongly correlated, often among subspecies defined by similar functions: lipid metabolism, hemostasis, antioxidant, or anti-inflammatory. Permutation analysis showed that the proteomes of 12 of the 16 subspecies differed significantly from that of total HDL. Conclusions- Taken together, correlation and permutation analyses support speciation of HDL. Functional studies of these novel subspecies and determination of their relation to diseases may provide new avenues to understand the HDL system of lipoproteins.

Perfluoroalkyl substances and changes in bone mineral density: A prospective analysis in the POUNDS-LOST study.

BACKGROUND: Recent studies suggested an inverse association between exposures to perfluoroalkyl substances (PFASs) and bone mineral density (BMD). Whether exposures to PFASs are also associated with changes in BMD has not been examined. METHODS: Five major PFASs (perfluorooctanesulfonic acid, PFOS; perfluorooctanoic acid, PFOA; perfluorohexanesulfonic acid, PFHxS; perfluorononanoic acid, PFNA; perfluorodecanoic acid, PFDA) and BMD (g/cm2) at six bone sites (spine, total hip, femoral neck, hip intertrochanteric area, hip trochanter, and hip Ward's triangle area) were measured at baseline among 294 participants in the POUNDS-LOST study, a weight-loss trial, of whom a total of 175 participants had BMD measured at both baseline and year 2. Linear regression was used to model the differences or changes in BMD for each SD increment of PFAS concentrations. In a secondary analysis, interactions between PFASs and baseline body mass index (BMI), as well as a BMI-related genetic risk score (GRS) derived from 97 BMI-predicting SNPs were examined in relation to changes in BMD. RESULTS: At baseline, both PFOS and PFOA were significantly associated with lower BMD at several sites. For each SD increase of PFOS, the ßs (95% CIs) for BMD were -0.020(-0.037, -0.003) for spine, -0.013(-0.026, 0.001) for total hip, -0.014(-0.028, 0.000) for femoral neck, and -0.013(-0.026, 0.000) for hip trochanter. For PFOA, the corresponding figures were -0.021(-0.038, -0.004) for spine, -0.015(-0.029, -0.001) for total hip, and -0.015(-0.029, -0.002) for femoral neck. After adjusting for baseline covariates and 2-year weight change, higher baseline plasma concentrations of PFOS, PFNA, and PFDA were associated with greater reduction in BMD in the hip; the ßs (95% CIs) were -0.005(-0.009, -0.001), -0.006(-0.010, -0.001), and -0.005(-0.009, -0.001), respectively. Similar associations were found in hip intertrochanteric area for all PFASs except PFHxS, with ßs ranging from -0.006 for PFOA to -0.008 for PFOS and PFNA. Participants with a higher GRS tended to have less PFAS-related BMD decline in total hip (Pinteraction = 0.005) and the hip intertrochanteric area (Pinteraction = 0.021). There were similar PFAS-related BMD changes by baseline BMI levels, although the interactions did not achieve statistical significance. CONCLUSIONS: This study demonstrated that higher plasma PFAS concentrations were not only associated with a lower BMD at baseline, but also a faster BMD loss in a weight-loss trial setting. Genetic predisposition to larger body size may somewhat attenuate the deleterious effects of PFASs on BMD. Further exploration of the possible impact of PFAS exposures on bone density is warranted.

Perfluoroalkyl substances and changes in body weight and resting metabolic rate in response to weight-loss diets: A prospective study.

BACKGROUND: The potential endocrine-disrupting effects of perfluoroalkyl substances (PFASs) have been demonstrated in animal studies, but whether PFASs may interfere with body weight regulation in humans is largely unknown. This study aimed to examine the associations of PFAS exposure with changes in body weight and resting metabolic rate (RMR) in a diet-induced weight-loss setting. METHODS AND FINDINGS: In the 2-year POUNDS Lost randomized clinical trial based in Boston, Massachusetts, and Baton Rouge, Louisiana, that examined the effects of energy-restricted diets on weight changes, baseline plasma concentrations of major PFASs were measured among 621 overweight and obese participants aged 30-70 years. Body weight was measured at baseline and 6, 12, 18, and 24 months. RMR and other metabolic parameters, including glucose, lipids, thyroid hormones, and leptin, were measured at baseline and 6 and 24 months. Participants lost an average of 6.4 kg of body weight during the first 6 months (weight-loss period) and subsequently regained an average of 2.7 kg of body weight during the period of 6-24 months (weight regain period). After multivariate adjustment, baseline PFAS concentrations were not significantly associated with concurrent body weight or weight loss during the first 6 months. In contrast, higher baseline levels of PFASs were significantly associated with a greater weight regain, primarily in women. In women, comparing the highest to the lowest tertiles of PFAS concentrations, the multivariate-adjusted mean weight regain (SE) was 4.0 (0.8) versus 2.1 (0.9) kg for perfluorooctanesulfonic acid (PFOS) (Ptrend = 0.01); 4.3 (0.9) versus 2.2 (0.8) kg for perfluorooctanoic acid (PFOA) (Ptrend = 0.007); 4.7 (0.9) versus 2.5 (0.9) kg for perfluorononanoic acid (PFNA) (Ptrend = 0.006); 4.9 (0.9) versus 2.7 (0.8) kg for perfluorohexanesulfonic acid (PFHxS) (Ptrend = 0.009); and 4.2 (0.8) versus 2.5 (0.9) kg for perfluorodecanoic acid (PFDA) (Ptrend = 0.03). When further adjusted for changes in body weight or thyroid hormones during the first 6 months, results remained similar. Moreover, higher baseline plasma PFAS concentrations, especially for PFOS and PFNA, were significantly associated with greater decline in RMR during the weight-loss period and less increase in RMR during the weight regain period in both men and women. Limitations of the study include the possibility of unmeasured or residual confounding by socioeconomic and psychosocial factors, as well as possible relapse to the usual diet prior to randomization, which could have been rich in foods contaminated by PFASs through food packaging and also dense in energy. CONCLUSIONS: In this diet-induced weight-loss trial, higher baseline plasma PFAS concentrations were associated with a greater weight regain, especially in women, possibly explained by a slower regression of RMR levels. These data illustrate a potential novel pathway through which PFASs interfere with human body weight regulation and metabolism. The possible impact of environmental chemicals on the obesity epidemic therefore deserves attention. TRIAL REGISTRATION: ClinicalTrials.gov NCT00072995.

Associations of anthropometry and lifestyle factors with HDL subspecies according to apolipoprotein C-III.

The presence of apoC-III on HDL impairs HDL's inverse association with coronary heart disease (CHD). Little is known about modifiable factors explaining variation in HDL subspecies defined according to apoC-III. The aim was to investigate cross-sectional associations of anthropometry and lifestyle with HDL subspecies in 3,631 participants from the Diet, Cancer, and Health study originally selected for a case-cohort study (36% women; age 50-65 years) who were all free of CHD. Greater adiposity and less activity were associated with higher HDL containing apoC-III and lower HDL lacking apoC-III. Per each 15 cm higher waist circumference, the level of HDL containing apoC-III was 2.8% higher (95% CI: 0.4, 5.3; P = 0.024) and the level of HDL not containing apoC-III was 4.7% lower (95% CI: -6.0, -3.4; P = <0.0001). Associations for physical activity were most robust to multivariable modeling. Each 20 metabolic equivalent task hours per week reported higher physical activity was associated with 0.9% (95% CI: -1.7, -0.1; P = 0.031) lower HDL containing apoC-III and 0.5% higher (95% CI: 0.1, 1.0; P = 0.029) HDL lacking apoC-III. Lower alcohol consumption was associated with lower HDL lacking apoC-III (percent difference per 15 g/day: 1.58 (95% CI: 0.84, 2.32; P = <0.0001). Adiposity and sedentary lifestyle were associated with a less favorable HDL subspecies profile.

Apolipoprotein A-II alters the proteome of human lipoproteins and enhances cholesterol efflux from ABCA1.

HDLs are a family of heterogeneous particles that vary in size, composition, and function. The structure of most HDLs is maintained by two scaffold proteins, apoA-I and apoA-II, but up to 95 other "accessory" proteins have been found associated with the particles. Recent evidence suggests that these accessory proteins are distributed across various subspecies and drive specific biological functions. Unfortunately, our understanding of the molecular composition of such subspecies is limited. To begin to address this issue, we separated human plasma and HDL isolated by ultracentrifugation (UC-HDL) into particles with apoA-I and no apoA-II (LpA-I) and those with both apoA-I and apoA-II (LpA-I/A-II). MS studies revealed distinct differences between the subfractions. LpA-I exhibited significantly more protein diversity than LpA-I/A-II when isolated directly from plasma. However, this difference was lost in UC-HDL. Most LpA-I/A-II accessory proteins were associated with lipid transport pathways, whereas those in LpA-I were associated with inflammatory response, hemostasis, immune response, metal ion binding, and protease inhibition. We found that the presence of apoA-II enhanced ABCA1-mediated efflux compared with LpA-I particles. This effect was independent of the accessory protein signature suggesting that apoA-II induces a structural change in apoA-I in HDLs.

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.

Plasma carotenoids and breast cancer risk in the Cancer Prevention Study II Nutrition Cohort.

PURPOSE: Several circulating carotenoids have been inversely associated with postmenopausal breast cancer risk in large cohort studies and a pooled analysis. Whether associations differ by tumor or participant characteristics remains unclear. We investigated the associations of plasma carotenoids with postmenopausal breast cancer risk overall and by estrogen receptor (ER) status, tumor stage, smoking status, and body mass index, in a case-control study nested in the Cancer Prevention Study II Nutrition Cohort. METHODS: A total of 496 invasive breast cancer cases diagnosed between blood draw in 1998-2001 and June 30, 2007 and matched 1:1 with controls on race, birth date, and blood draw date were included. Multivariable-adjusted conditional and unconditional logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Plasma α-carotene above the lowest quartile was associated with significant 40-43% lower risk of invasive breast cancer risk (fourth vs. first quartile OR 0.60, 95% CI 0.41-0.87, P-trend = 0.037) after adjustment for multiple covariates. This inverse association was strengthened after further adjustment for other plasma carotenoids and total fruit and vegetable intake (fourth vs. first quartile OR 0.50, 95% CI 0.29-0.85, P-trend = 0.041). Other plasma carotenoids or total carotenoids were not associated with breast cancer risk. The inverse association of α-carotene with breast cancer remained for ER+, but not for ER- tumors, although test for heterogeneity was not statistically significant (P-heterogeneity = 0.49). CONCLUSIONS: These results suggest that higher plasma α-carotene is associated with lower risk of invasive breast cancer.