Eke G. Gruppen

GlycA, a marker of acute phase glycoproteins, and the risk of incident type 2 diabetes mellitus: PREVEND study

BACKGROUND GlycA is a recently developed glycoprotein biomarker of systemic inflammation that may be predictive of incident type 2 diabetes mellitus (T2DM). METHODS Analytical performance of the GlycA test, measured on the Vantera® Clinical Analyzer, was evaluated. To test its prospective association with T2DM, GlycA was measured in 4524 individuals from the PREVEND study and a survival analysis was performed with a mean follow-up period of 7.3y. RESULTS Imprecision for the GlycA test ranged from 1.3-2.3% and linearity was established between 150 and 1588μmol/l. During the follow-up period, 220 new T2DM cases were ascertained. In analyses adjusted for relevant covariates, GlycA was associated with incident T2DM; hazard ratio (HR) for the highest vs. lowest quartile 1.77 [95% Confidence Interval (CI): 1.10-2.86, P=0.01], whereas the association of high sensitivity C-reactive protein (hsCRP) with T2DM was not significant. GlycA remained associated with incident T2DM after additional adjustment for hsCRP; HR 1.71 [1.00-2.92, P=0.04]. A multivariable adjusted analysis of dichotomized subgroups showed that the hazard for incident T2DM was highest in the subgroup with high GlycA and low hsCRP (P=0.03). CONCLUSIONS The performance characteristics of the GlycA test reveal that it is suitable for clinical applications, including assessment of the risk of future T2DM.

GlycA, a Pro-Inflammatory Glycoprotein Biomarker, and Incident Cardiovascular Disease: Relationship with C-Reactive Protein and Renal Function.

Objective GlycA is a novel nuclear magnetic resonance spectroscopy-measured biomarker of systemic inflammation. We determined whether GlycA is associated with incident cardiovascular disease (CVD) in men and women, examined whether this association with CVD is modified by renal function, and compared this association with high sensitivity C-reactive protein (hsCRP). Research design and methods A prospective cohort study was performed among 4,759 subjects (PREVEND study) without a history of CVD and cancer. Incident CVD was defined as the combined endpoint of cardiovascular morbidity and mortality. Cox regression analyses were used to examine associations of baseline GlycA and hsCRP with CVD. Results 298 first CVD events occurred during a median follow-up of 8.5 years. After adjustment for clinical and lipid measures the hazard ratio (HR) for CVD risk in the highest GlycA quartile was 1.58 (95% CI, 1.05–2.37, P for trend = 0.004). This association was similar after further adjustment for renal function (estimated glomerular filtration rate and urinary albumin excretion). After additional adjustment for hsCRP, GlycA was still associated with incident CVD (HR: 1.16 per SD change (95% CI, 1.01–1.33), P = 0.04). Similar results were obtained for hsCRP (HR per SD change after adjustment for GlycA: 1.17 (95% CI 1.17 (95% CI, 1.01–3.60), P = 0.04). CVD risk was highest in subjects with simultaneously higher GlycA and hsCRP (fully adjusted HR: 1.79 (95% CI, 1.31–2.46), P<0.001). Conclusion GlycA is associated with CVD risk in men and women, independent of renal function. The association of GlycA with incident CVD is as strong as that of hsCRP.

Inflammatory glycoproteins in cardiometabolic disorders, autoimmune diseases and cancer

The physiological function initially attributed to the oligosaccharide moieties or glycans on inflammatory glycoproteins was to improve protein stability. However, it is now clear that glycans play a prominent role in glycoprotein structure and function and in some cases contribute to disease states. In fact, glycan processing contributes to pathogenicity not only in autoimmune disorders but also in atherosclerotic cardiovascular disease, diabetes and malignancy. While most clinical laboratory tests measure circulating levels of inflammatory proteins, newly developed diagnostic and prognostic tests are harvesting the information that can be gleaned by measuring the amount or structure of the attached glycans, which may be unique to individuals as well as various diseases. As such, these newer glycan-based tests may provide future means for more personalized approaches to patient stratification and improved patient care. Here we will discuss recent progress in high-throughput laboratory methods for glycomics (i.e. the study of glycan structures) and glycoprotein quantification by methods such as mass spectrometry and nuclear magnetic resonance spectroscopy. We will also review the clinical utility of glycoprotein and glycan measurements in the prediction of common low-grade inflammatory disorders including cardiovascular disease, diabetes and cancer, as well as for monitoring autoimmune disease activity.

GlycA, a biomarker of inflammatory glycoproteins, is more closely related to the leptin/adiponectin ratio than to glucose tolerance status

OBJECTIVES Plasma GlycA is a recently developed biomarker whose nuclear magnetic resonance signal originates from glycosylated acute-phase proteins. The aim of our study was to determine potential relationships between GlycA and adiposity, insulin resistance (HOMA(ir)), high sensitive C-reactive protein (hs-CRP), leptin, adiponectin, and the leptin/adiponectin ratio, and to test whether GlycA is elevated in subjects with impaired fasting glucose (IFG) and type 2 diabetes mellitus (T2DM). DESIGN AND METHODS Plasma GlycA, hs-CRP, leptin, adiponectin, the leptin/adiponectin ratio, and insulin resistance (HOMA(ir)) were measured in 103 fasting subjects (30 with normal fasting glucose, 25 with IFG and 48 with T2DM). RESULTS In all subjects combined, plasma GlycA was correlated positively with body mass index (BMI), HOMA(ir), hs-CRP, leptin and the leptin/adiponectin ratio, and inversely with adiponectin (p < 0.05 to p < 0.001). GlycA did not significantly vary according to glucose tolerance category (p = 0.060). GlycA was related positively to the leptin/adiponectin ratio (p = 0.049), independent of BMI (p = 0.056) and HOMA(ir) (p = 0.50). CONCLUSIONS High plasma GlycA reflects a pro-inflammatory state. Adipose tissue-associated inflammatory processes could contribute to increased circulating levels of glycosylated acute-phase proteins.

A novel protein glycan biomarker and LCAT activity in metabolic syndrome.

The cholesterol‐esterifying enzyme, lecithin:cholesterol acyltransferase (LCAT), is instrumental in high‐density lipoprotein (HDL) remodelling. LCAT may also modify oxidative and inflammatory processes, as supported by an inverse relationship with HDL antioxidative functionality and a positive relationship with high‐sensitivity C‐reactive protein (hsCRP). GlycA is a recently developed proton nuclear magnetic resonance (NMR) spectroscopy‐measured biomarker of inflammation whose signal originates from a subset of N‐acetylglucosamine residues on the most abundant glycosylated acute‐phase proteins. Plasma GlycA correlates positively with hsCRP and may predict cardiovascular disease even independent of hsCRP. Here, we tested the extent to which plasma GlycA is elevated in metabolic syndrome (MetS), and determined its relationship with LCAT activity.

A pro-inflammatory glycoprotein biomarker is associated with lower bilirubin in metabolic syndrome

OBJECTIVES Bilirubin exerts anti-oxidative and anti-inflammatory properties which may beneficially influence the development of cardio-metabolic disorders. A nuclear magnetic resonance (NMR) spectroscopy-based glycoprotein biomarker, designated GlycA, whose signal originates from several glycosylated acute-phase proteins, has been recently developed. We tested whether plasma GlycA is associated with bilirubin in subjects with and without MetS. DESIGN AND METHODS GlycA (NMR spectroscopy), high sensitivity C-reactive protein (hs-CRP) and bilirubin were measured in 58 fasting subjects with MetS and in 63 subjects without MetS (including 65 subjects with type 2 diabetes mellitus). RESULTS GlycA and hs-CRP were higher, coinciding with lower bilirubin in MetS (p<0.01 for each). In all subjects combined, GlycA was strongly correlated with hs-CRP (r=0.631, p<0.001). Age-, sex- and diabetes status-adjusted multivariable linear regression analysis demonstrated that GlycA and hs-CRP were both associated positively with the presence of MetS (β=0.256, p=0.014 and β=0.259, p=0.012, respectively). GlycA and hs-CRP were negatively related to bilirubin (β=-0.258, p=0.007 and β=-0.305, p<0.001, respectively), independent of MetS (p>0.05 for each) and diabetes status (p>0.50 for each). CONCLUSIONS GlycA is elevated in MetS, and may represent a quantitative measure of a pro-inflammatory state. Increased levels of glycosylated acute-phase proteins are associated with lower bilirubin in MetS.

TMAO is Associated with Mortality: Impact of Modestly Impaired Renal Function

Trimethylamine-N-Oxide (TMAO) is a microbiome-related metabolite that is cleared by the kidney and linked to renal function. We explored the relationship between TMAO and all-cause mortality, and determined whether this association was modified by renal function. A prospective study was performed among PREVEND participants to examine associations of plasma TMAO with all-cause mortality. After median follow-up of 8.3 years in 5,469 participants, 322 subjects died. TMAO was positively associated with age, body mass index, type 2 diabetes mellitus and inversely with estimated glomerular filtration rate (eGFRcreatcysC)(all P < 0.001). Subjects in the highest versus lowest TMAO quartile had a crude 1.86-fold higher mortality risk (Ptrend < 0.001). After adjustment for several risk factors, TMAO remained associated with all-cause mortality [HR:1.36 (95% CI, 0.97–1.91),Ptrend = 0.016]. This association was lost after further adjustment for urinary albumin excretion and eGFR [HR:1.15 (95% CI, 0.81–1.64),Ptrend = 0.22]. The association of TMAO with mortality was modified by eGFR in crude and age- and sex-adjusted analyses (interaction P = 0.002). When participants were stratified by renal function (eGFR < vs. ≥90 mL/min/1.73 m2), TMAO was associated with all-cause mortality only in subjects with eGFR <90 mL/min/1.73 m2 [adjusted HR:1.18 (95% CI, 1.02–1.36),P = 0.023]. In conclusion, TMAO is associated with all-cause mortality, particularly in subjects with eGFR <90 mL/min/1.73 m2.

Paraoxonase-1 activity is positively related to phospholipid transfer protein activity in type 2 diabetes mellitus : Role of large HDL particles

OBJECTIVES High density lipoprotein (HDL)-associated paraoxonase-1 (PON-1) exerts anti-oxidative properties, whereas phospholipid transfer protein (PLTP) is able to convert mature HDL into larger and smaller HDL particles. Here we tested associations of PON-1 with PLTP in type 2 diabetes mellitus (T2DM), a condition characterized by lower PON-1 activity and higher PLTP activity. DESIGN AND METHODS Serum PON-1 (arylesterase activity), plasma PLTP activity (liposome-vesicle HDL system), and (apo)lipoproteins were measured in 81 T2DM subjects (mean age 59±9years; 31 women; no insulin treatment). In 48 participants, HDL subfractions were measured by nuclear magnetic resonance spectroscopy. RESULTS In univariate correlation analysis, PON-1 activity was positively related to PLTP activity (r=0.348, p=0.001). PLTP activity was positively related to blood pressure, body mass index and triglycerides, whereas PON-1 activity was positively to HDL cholesterol and apoA-I (p<0.05 to <0.01 for each). Both PLTP activity and PON-I activity were positively related to large HDL particles (r=0.379, p=0.008 and r=0.411, p=0.004, respectively). In multivariable linear regression analysis, PON-1 activity was associated with PLTP activity independent of clinical covariates and HDL cholesterol or apoA-I (β=0.340, p=0.001 and β=0.320, p=0.003, respectively). The association of PON-1 activity with PLTP activity was lost in analysis which included large HDL particles (large HDL: β=0.411, p=0.004). CONCLUSIONS PON-1 activity is positively related to PLTP activity in T2DM, raising the possibility that PLTP could act to maintain PON-1. This association may in part be attributable to a common relationship of PON-1 and PLTP with large HDL particles.

Plasma apoE is Elevated in Metabolic Syndrome: Importance of Large Very LowDensity and Low Density Lipoprotein Particles

Background: Apolipoprotein E (apoE) is carried by all major lipoprotein classes in plasma and is likely to contribute to the development of atherosclerosis. We set out to determine the extent to which plasma apoE is related to various VLDL, LDL and HDL subfractions in subjects with and without metabolic syndrome (MetS). Methods: Plasma lipids, lipoprotein subfractions (nuclear magnetic resonance spectroscopy) and plasma apoE were determined in 60 subjects with and 62 subjects without MetS (APOE e2/e2 carriers excluded). Results: Plasma apoE was higher in MetS, coinciding with increased total and large VLDL particles, as well as total LDL particles (p 0.30). Plasma apoE was unrelated to HDL particle concentration (p=0.88). Conclusions: Plasma apoE is elevated in MetS in conjunction with increased concentrations of (large) VLDL and LDL particles. These novel findings provide a rationale to explore whether preferential association of apoE with (large) VLDL and LDL could modify its influence on atherosclerosis development.

Plasma phospholipid transfer protein activity is inversely associated with betaine in diabetic and non-diabetic subjects.

BackgroundThe choline metabolite, betaine, plays a role in lipid metabolism, and may predict the development of cardiovascular disease and type 2 diabetes mellitus (T2DM). Phospholipid transfer protein (PLTP) and lecithin:cholesterol acyltransferase (LCAT) require phosphatidylcholine as substrate, raising the possibility that there is an intricate relationship of these protein factors with choline metabolism. Here we determined the relationships of PLTP and LCAT activity with betaine in subjects with and without T2DM.MethodsPlasma betaine (nuclear magnetic resonance spectroscopy), PLTP activity (liposome-vesicle HDL system), LCAT activity (exogenous substrate assay) and (apo)lipoproteins were measured in 65 type 2 diabetic (T2DM) and in 55 non-diabetic subjects.ResultsPLTP and LCAT activity were elevated in T2DM (p < 0.05), whereas the difference in betaine was not significant. In age-, sex- and diabetes status-controlled correlation analysis, betaine was inversely correlated with triglycerides and positively with HDL cholesterol (p < 0.05 to 0.01). PLTP and LCAT activity were positively correlated with triglycerides and inversely with HDL cholesterol (p < 0.05 to 0.001). PLTP (r = −0.245, p = 0.006) and LCAT activity (r = −0.195, p = 0.035) were correlated inversely with betaine. The inverse association of PLTP activity with betaine remained significant after additional adjustment for body mass index and lipoprotein variables (β = −0.179, p = 0.034), whereas its association with LCAT activity lost significance (β = −0.056, p = 0.44).ConclusionsBetaine may influence lipoprotein metabolism via an effect on PLTP activity.