Analysis Of Lipoprotein Subclasses Research Articles

Abstract P106: Stabilization Muscles Drive Associations Between Lipoproteins And Total Abdominal Muscle And Intermuscular Adipose Tissue In The Multi-ethnic Study Of Atherosclerosis

Introduction: Quality and quantity of skeletal muscle decrease with age, largely due to adipose tissue infiltration, and are important determinants of metabolic health. To inform efforts to slow aging-related decline in muscle mass and prevent myosteatosis, a better understanding of the biological determinants of muscle atrophy and quality is needed. We used targeted lipidomics to identify, with a greater specificity, lipoproteins associated with muscle and intermuscular adipose tissue (IMAT) area (quantity) and density (quality) of the total abdominal, locomotion, and stabilization muscles in the Multi-Ethnic Study of Atherosclerosis. Hypothesis: Lower density lipoproteins will be positively associated with muscle and IMAT quantity, but negatively associated with quality. Methods: At visit one, 105 serum lipoproteins were measured by Bruker lipoprotein subclass analysis with 1 H-Nuclear Magnetic Resonance spectroscopy. Muscle and IMAT area (cm 2 ) and density (Hounsfield units) were estimated 2.6 years, on average, after visit 1 for the total abdominal, locomotion (psoas), and stabilization (paraspinal, oblique, and rectus abdominis) muscles from computed-tomography scans at the L4/L5 spinal junction. We identified lipoproteins associated with body composition using linear regression adjusting for age, gender, race, diet, physical activity, lipid-lowering medication, and multiple comparisons using a 1% false discovery rate. Results: Participants (N=947) were 44-84 years old (mean: 63), 51% men, 40% White, 16% Black, 16% Chinese American, and 27% Hispanic American. Among 105 lipoproteins, 24 were associated with total muscle area, whereas none were associated with muscle density. When examining specific muscle groups, 25 lipoproteins were associated with stabilization muscle area, driven by the oblique muscles. As for total IMAT area, there were 27 associations with lipoproteins. Specifically, 27 lipoproteins were associated with stabilization muscle IMAT area, driven by oblique and rectus abdominis muscles. Last, 39 lipoproteins were associated with total IMAT density, with 28 and 33 associated with locomotion and stabilization (driven by obliques) IMAT density, respectively. Higher VLDL: cholesterols, free cholesterols, phospholipids, and triglycerides and lower HDL: cholesterols and free cholesterols were associated with higher muscle area and IMAT area, but lower IMAT density (

Metabolomic aging and its association with depression in a UK cohort

Introduction Depression is associated with both reduced lifespan and cardiovascular disease risk. Accelerated biological aging may underlie this association. Modern ‘omics’ platforms provide new opportunities for the systematic assessment of biological aging. Genome-wide DNA methylation data has been used to predict chronological age with high accuracy, and ‘age acceleration’ - the difference between DNA methylation age and chronological age - is predictive of mortality. Few studies have employed metabolomics (small molecule profiling) to model the aging process. We have employed untargeted metabolomics across multiple nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) based platforms, to develop a highly predictive model of age, within a large sample from the Airwave Health Monitoring Study (AIRWAVE). We investigate the correlation between metabolomic age and DNA methylation age and show that metabolic age acceleration is associated with depression and other disease risk factors. Methods Full metabolomic data was acquired for 2238 participants (age range: 19.2–65.2 years, 61% male) in the AIRWAVE cohort of employees of police forces from across Great Britain. Nine metabolomic analyses were applied: NMR, hydrophilic interaction chromatography-MS and reversed-phase chromatography-MS (both positive and negative modes) in both serum and urine, and NMR-based Bruker IVDr Lipoprotein Subclass Analysis in serum only. NMR profiles were aligned and interpolated onto a common 20,000-point grid while MS data was processed into retention time-m/z pairs. All platforms were combined into one dataset providing 98,824 metabolic features. A metabolomic age prediction model was constructed using elastic net modelling, with penalisation parameters found following 10-fold cross validation, in a training portion of the data (80% of participants) and then validated in a test set (remaining 20%). Metabolic age acceleration (AA) was defined as the difference between predicted metabolomic and chronological age. We computed the ‘intrinsic’ AA, defined as the residuals from the linear regression of AA with chronological age, hereafter referred to as ‘metAA’. DNA methylation was measured in leukocytes in 1102 participants using the Illumina 850 K methylationEPIC array and Hannum's DNA methylation age calculated. Intrinsic DNA methylation AA was calculated as for metAA, additionally accounting for blood cell proportion, and referred to as ‘DNAmethAA’. Depression was assessed through the Patient Health Questionnaire (PHQ-9) and associations with metAA and DNA methAA were assessed through linear regression. Results Metabolomic age, based on 472 features, was highly correlated both with chronological age in the independent validation set (Pearson's correlation r = 0.85) and with DNA methylation age ( r = 0.85). There was no relationship between DNAmethAA and metAA ( r = 0.02). In analyses adjusted for sex, disease risk factors and diet, metAA was associated with both having some depressive symptoms [β, interpretable as years of increase in metabolic age, = 0.70, 95% confidence interval (CI): 0.38, 1.01] and being a depression case (0.54, 95% CI: 0.08, 0.99) compared to those with no symptoms of depression. Obesity (1.35, 95% CI: 0.95, 1.69); low income (0.33, 95% CI: 0.00, 0.65); and heavy drinking (0.72, 95% CI: 0.08, 1.36) were also associated with metAA. Only being male was significantly associated with DNAmethAA (0.89, 95% CI: 0.47, 1.30). Participants with low income had higher DNAmethAA than those with high income, although this was not statistically significant [0.41 (−0.12, 0.94) after adjustment for sex]. Conclusion Metabolomic analysis can be used to predict age with high accuracy. Accelerated metabolic aging appears to capture a different dimension of the aging process to DNA methylation age acceleration, and may contribute to associations between depression and mortality.

Multivariate DoE Optimization of Asymmetric Flow Field Flow Fractionation Coupled to Quantitative LC-MS/MS for Analysis of Lipoprotein Subclasses

In this report we demonstrate a practical multivariate design of experiment (DoE) approach for asymmetric flow field-flow fractionation (AF4) method optimization using separation of lipoprotein subclasses as an example. First, with the aid of commercially available software, we built a full factorial screening design where the theoretical outcomes were calculated by applying established formulas that govern AF4 channel performance for a 5–35 nm particle size range of interest for lipid particles. Second, using the desirable ranges of instrumental parameters established from theoretical optimization, we performed fractional factorial DoE for AF4 separation of pure albumin and ferritin with UV detection to narrow the range of instrumental parameters and allow optimum size resolution while minimizing losses from membrane immobilization. Third, the optimal range of conditions were tested using response surface DoE for sub-fractionation of high and low density lipoproteins (HDL and LDL) in human serum, where the recovery of the analytes were monitored by fraction collection and isotope-dilution LC-MS/MS analysis of each individual fraction for cholesterol and apolipoproteins (ApoA-1 and ApoB-100). Our results show that DoE is an effective tool in combining AF4 theoretical knowledge and experimental data in finding the most optimal set of AF4 instrumental parameters for quantitative coupling with LC-MS/MS measurements.

Associations among smoking status, lifestyle and lipoprotein subclasses

The relationship between cigarette smoking and cardiovascular disease is well established, yet the underlying mechanisms remain unclear. Although smokers have a more atherogenic lipid profile, this may be mediated by other lifestyle-related factors. Analysis of lipoprotein subclasses by the use of nuclear magnetic resonance spectroscopy (NMR) may improve characterisation of lipoprotein abnormalities. We used NMR spectroscopy to investigate the relationships between smoking status, lifestyle-related risk factors, and lipoproteins in a contemporary cohort. A total of 612 participants (360 women) aged 40-69 years at baseline (1990-1994) enrolled in the Melbourne Collaborative Cohort Study had plasma lipoproteins measured with NMR. Data were analysed separately by sex. After adjusting for lifestyle-related risk factors, including alcohol and dietary intake, physical activity, and weight, mean total low-density lipoprotein (LDL) particle concentration was greater for female smokers than nonsmokers. Both medium- and small-LDL particle concentrations contributed to this difference. Total high-density lipoprotein (HDL) and large-HDL particle concentrations were lower for female smokers than nonsmokers. The proportion with low HDL particle number was greater for female smokers than nonsmokers. For men, there were few smoking-related differences in lipoprotein measures. Female smokers have a more atherogenic lipoprotein profile than nonsmokers. This difference is independent of other lifestyle-related risk factors. Lipoprotein profiles did not differ greatly between male smokers and nonsmokers.

Clinical Use of a Carbohydrate-Restricted Diet to Treat the Dyslipidemia of the Metabolic Syndrome

The metabolic syndrome is characterized by an atherogenic dyslipidemia identifiable using lipoprotein subclass analysis. This study assesses the effect of a carbohydrate-restricted diet on the dyslipidemia of the metabolic syndrome in a clinical setting. This is a retrospective chart review of patients attending a preventive medicine clinic using lipoprotein subclass analysis (by NMR spectroscopy) to identify the atherogenic dyslipidemia. If present, patients were counseled to begin a carbohydrate-restricted diet (< 20 g/day). Patients already on statin therapy were included only if the medication dose was not changed. The outcomes were changes in body weight, fasting serum lipid profiles and serum lipoprotein subclasses. Of 122 patients identified, 80 patients had complete pre- and post-treatment data. The mean (+/-SD) age was 66 +/- 9 years, baseline weight was 85 +/- 12 kg, BMI was 28.1 +/- 3.6, 73% were male, 99% were Caucasian. Sixty-five percent were taking statin medication. Carbohydrate-restriction led to a 13% reduction in total cholesterol, 16% reduction in LDL cholesterol, 38% reduction in triglycerides, and a 13% increase in HDL cholesterol (all p values < 0.001). Carbohydrate-restriction also led to a reduction in LDL particle concentration of 28%, a reduction in small LDL of 82%, a reduction of large VLDL of 62%, and an increase in large HDL of 30% (all p values < 0.001). A carbohydrate-restricted diet recommendation led to improvements in lipid profiles and lipoprotein subclass traits of the metabolic syndrome in a clinical outpatient setting, and should be considered as a treatment for the metabolic syndrome.

Lipoprotein subclass profiles of hyperlipidemic diabetic mice measured by nuclear magnetic resonance spectroscopy

Dyslipidemia accelerates vascular complications of diabetes. Nuclear magnetic resonance (NMR) analysis of lipoprotein subclasses is used to evaluate a mouse model of human familial hypercholesterolemia +/- streptozotocin (STZ)-induced diabetes. A double knockout (DKO) mouse (low-density lipoprotein receptor [LDLr] -/-; apolipoprotein B [apoB] mRNA editing catalytic polypeptide-1 [Apobec1] -/-) was studied. Wild-type (WT) and DKO mice received sham or STZ injections at age 7 weeks, yielding control (WT-C, DKO-C) and diabetic (WT-D, DKO-D) groups. Fasting serum was collected when the mice were killed (age 40 weeks) for Cholestech analysis (Cholestech Corp, Hayward, CA) and NMR lipoprotein subclass profile. By Cholestech, fasting triglyceride and total cholesterol increased in DKO-C versus WT-C. Diabetes further increased total cholesterol in DKO. High-density lipoprotein cholesterol (HDL-C) was similar among all groups. NMR revealed that LDL in all groups was present in a subclass the size of large human LDL and was increased 48-fold in DKO-C versus WT-C animals, but was unaffected by diabetes. HDL was found in a subclass equivalent to large human HDL, and was similar among groups. In conclusion, NMR analysis reveals lipoprotein subclass distributions and the effects of genetic modification and diabetes in mice, but lack of particles the size of human small LDL and small HDL may limit the relevance of the present animal model to human disease.

Changes in the profile of lipoprotein subfractions associated with hormone replacement therapy

To report the effects of 2 regimens of hormone replacement therapy during the postmenopausal period on the profile of the major lipoprotein subfractions (HDL, LDL, and VLDL). We carried out a cohort study in 38 postmenopausal patients who were starting their hormone replacement therapy due to gynecological indications, for a period of 12 weeks. Analysis of lipoprotein subclasses was performed through nuclear magnetic resonance spectroscopy. Hormone replacement therapy cause an increase in the proportion of larger subfractions of VLDL and HDL (p=0.008 and 0.03, respectively) and in the proportion of larger particles of VLDL due to a 36% increase in the levels of larger particles (p=0.004), concomitantly with a 15% reduction in the levels of smaller particles (p=0.04). In regard to HDL, the increase occurred only a 17% increase in the levels of larger particles (p=0.002). No significant change occurred in the distribution pattern of LDL subfractions. The proportion of larger subfractions of VLDL and HDL increases after hormone replacement therapy. The increase in the proportion of larger particles of VLDL occurs due to an increase in the levels of the larger subclasses concomitantly with a reduction in the smaller particles. However, an increase in the proportion of larger particles of HDL occurs only due to an increase in the levels of the larger subfractions.

Levels and correlates of LDL and VLDL particle sizes among children: the Bogalusa heart study

Levels of lipids and lipoproteins among children vary by sex and race/ethnicity, and are correlated with age, obesity, and other characteristics. There is, however, little information on the distribution and correlates of low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) subclasses in early life. We used nuclear magnetic resonance (NMR) spectroscopy to determine mean LDL and VLDL particle sizes among 10- to 17-year-olds ( n=918) who participated in the 1992–94 examination of the Bogalusa heart study. As compared with girls, boys had a smaller (0.1 nm) mean LDL particle size and a larger (0.9 nm) mean VLDL size; furthermore, the average size of VLDL particles increased with age among white boys but not among other children. Although there were also black/white differences in particle sizes, with black children having larger LDL and smaller VLDL particles, these racial contrasts could be attributed to differences in lipid levels. Levels of triglycerides, insulin, and relative weight were associated with the size of VLDL (positive) and LDL (negative) particles. These results suggest that the analysis of lipoprotein subclasses may provide a better understanding of the role of various risk factors in the development of coronary heart disease