Serum platelet-activating factor acetylhydrolase activity: A novel potential inflammatory marker in type 1 diabetes

Evaluation of lipoprotein-associated phospholipase A2 as a marker for renal microvasculopathy in adolescents with Type 1 diabetes

AIM

To assess the relevance of lipoprotein-associated phospholipase A2 activity as a diagnostic and prognostic marker for renal microvascular diseases.

METHODS

We analysed lipoprotein-associated phospholipase A2 activity and lysophosphatidylcholine levels (as a surrogate marker of oxidative stress) in 165 adolescents (aged 17.0 ± 2.3 years) with a history of Type 1 diabetes greater than 10 years. Clinical data were obtained from the German/Austrian nationwide Diabetes-Patients Follow-up (DPV) registry at blood collection and on average 2.4 ± 1.3 years later at follow-up. Relationships between lipoprotein-associated phospholipase A2 activity and clinical, demographic and laboratory variables, lysophosphatidylcholine levels and presence of albuminuria were evaluated by multivariable linear and logistic regression.

RESULTS

Lipoprotein-associated phospholipase A2 activity was higher in male than female adolescents (P = 0.002). Albuminuria was present in 14% (22/158) of participants at baseline, and 5% (4/86) of participants without albuminuria at baseline developed albuminuria until follow-up. Lipoprotein-associated phospholipase A2 activity was associated neither with present nor with incident albuminuria. Lysophosphatidylcholine did not correlate with lipoprotein-associated phospholipase A2 activity. Cross-sectional bivariate correlation as well as multivariable linear regression analysis revealed a negative correlation of lipoprotein-associated phospholipase A2 activity with HbA_1c and HDL-cholesterol.

CONCLUSIONS

Lipoprotein-associated phospholipase activity was not associated with surrogate markers for oxidative stress and early diabetic nephropathy. The association of decreased lipoprotein-associated phospholipase A2 activity with poor glucose control might limit its function as a predictor of micro- and macrovascular diseases in Type 1 diabetes.

Temporal expression profiling of plasma proteins reveals oxidative stress in early stages of Type 1 Diabetes progression

Blood markers other than islet autoantibodies are greatly needed to indicate the pancreatic beta cell destruction process as early as possible, and more accurately reflect the progression of Type 1 Diabetes Mellitus (T1D). To this end, a longitudinal proteomic profiling of human plasma using TMT-10plex-based LC-MS/MS analysis was performed to track temporal proteomic changes of T1D patients (n=11) across 9 serial time points, spanning the period of T1D natural progression, in comparison with those of the matching healthy controls (n=10). To our knowledge, the current study represents the largest (>2000 proteins measured) longitudinal expression profiles of human plasma proteome in T1D research. By applying statistical trend analysis on the temporal expression patterns between T1D and controls, and Benjamini-Hochberg procedure for multiple-testing correction, 13 protein groups were regarded as having statistically significant differences during the entire follow-up period. Moreover, 16 protein groups, which play pivotal roles in response to oxidative stress, have consistently abnormal expression trend before seroconversion to islet autoimmunity. Importantly, the expression trends of two key reactive oxygen species-decomposing enzymes, Catalase and Superoxide dismutase were verified independently by ELISA.

BIOLOGICAL SIGNIFICANCE

The temporal changes of >2000 plasma proteins (at least quantified in two subjects), spanning the entire period of T1D natural progression were provided to the research community. Oxidative stress related proteins have consistently different dysregulated patterns in T1D group than in age-sex matched healthy controls, even prior to appearance of islet autoantibodies - the earliest sign of islet autoimmunity and pancreatic beta cell stress.

Lipoprotein-associated phospholipase A2 activity and low-density lipoprotein subfractions after a 2-year treatment with atorvastatin in adolescents with type 1 diabetes

BACKGROUND

The objective of the study was to assess the effect of atorvastatin on inflammation markers and low-density lipoprotein (LDL) subfractions.

METHODS

In a prospective, randomized, double-blind pilot study involving 28 adolescents with type 1 diabetes (T1D), lipoprotein-associated phospholipase A2 (Lp-PLA2) activity, high-sensitivity C-reactive protein (hsCRP), and subfractions of LDL were measured at baseline, after 1 year and 2 years of treatment with atorvastatin (10 mg/day) vs. placebo.

RESULTS

For the atorvastatin group, we found posttreatment reductions of Lp-PLA2 activity (p<0.001), LDL cholesterol (p=0.001), non-small dense LDL cholesterol (p<0.001), total cholesterol (p<0.001), and apolipoprotein B (apo B) (p<0.001), whereas small dense LDL cholesterol and hsCRP did not change significantly.

CONCLUSIONS

In adolescents with T1D, long-term treatment with atorvastatin is safe and may reduce cardiovascular risk by significant decreases of Lp-PLA2 activity and LDL cholesterol.

"Association between platelet activating factor acetylhydrolase and diabetic retinopathy: Does inflammation affect the retinal status?"

AIM

To assess the role of plasma platelet activating factor acetylhydrolase (PAF-AH) in pathogenesis and progression of diabetic retinopathy (DR).

MATERIALS AND METHODS

Sixty eight diabetics and 23 age-frequency-matched non-diabetic patients underwent blood sampling and the plasma PAF-AH activity was calculated. The diabetic patients were further classified into two groups, according to the Early Treatment Diabetic Retinopathy Study (ETDRS) classification, based on indirect fundoscopy and fluorescein angiography. Thirty seven patients with non-proliferative DR (NPDR) and 31 patients with proliferative DR (PDR) were finally included in the study.

RESULTS

The plasma PAF-AH activity was increased in diabetic patients with PDR (0.206 μmol/min/ml) compared to control group (0.114 μmol/min/ml, post-hoc Bonferroni comparison test: p<0.0001) and to NPDR group (0.147 μmol/min/ml, post-hoc Bonferroni comparison test: p=0.012).

CONCLUSIONS

The activity of PAF-AH in the plasma increases in parallel with DR severity.

Higher circulating GlycA, a pro-inflammatory glycoprotein biomarker, relates to lipoprotein-associated phospholipase A2 mass in nondiabetic subjects but not in diabetic or metabolic syndrome subjects

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a cardiovascular risk marker, which is in part complexed to low-density lipoproteins, where it exerts pro-inflammatory properties. GlycA is a pro-inflammatory proton nuclear magnetic resonance spectroscopy biomarker whose signal originates from a subset of N-acetylglucosamine residues on the most abundant glycosylated acute-phase proteins.

OBJECTIVE

We compared plasma GlycA and Lp-PLA2 mass between subjects without type 2 diabetes mellitus (T2DM) or the metabolic syndrome (MetS) and subjects with T2DM and/or MetS. We also tested the relationship of GlycA with Lp-PLA2 in each group.

METHODS

Plasma GlycA, Lp-PLA2 mass, high-sensitivity C-reactivity protein (hsCRP) and lipids were measured in 40 subjects with neither T2DM nor MetS (group 1) and in 58 subjects with T2DM and/or MetS (group 2).

RESULTS

GlycA and hsCRP were higher (P < .01 for each), whereas Lp-PLA2 was lower in group 2 vs group 1 (P < .001). GlycA was positively related to hsCRP in each group (P < .001). In contrast, GlycA was correlated positively with Lp-PLA2 in group 1 (r = 0.384, P = .015), but not in group 2 (r = 0.045; P = .74; interaction term for difference: P = .059). Although Lp-PLA2 was correlated positively with non-high-density lipoprotein cholesterol and low-density lipoprotein cholesterol in each group (P ≤ .02), its inverse relationship with high-density lipoprotein cholesterol in group 1 (r = -0.381, P = .013) was absent in group 2 (r = -0.101, P = .42).

CONCLUSIONS

A pro-inflammatory glycoprotein biomarker, GlycA, is higher in subjects with either T2DM, MetS, or both. The normally present positive relationship of GlycA with Lp-PLA2 is blunted in subjects with T2DM and/or MetS.

PAF and its metabolic enzymes in healthy volunteers: interrelations and correlations with basic characteristics

PAF (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine), a potent inflammatory mediator, is synthesized via the remodeling and the de novo route, key enzymes of which are acetyl-CoA:lyso-PAF acetyltransferase (lyso-PAF-AT) and DTT-insensitive CDP-choline:1-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase (PAF-CPT), respectively. PAF-acetylhydrolase (PAF-AH) and its extracellular isoform lipoprotein-associated phospholipase-A(2) (Lp-PLA(2)) catabolize PAF. This study evaluated PAF levels together with leukocyte PAF-CPT, lyso-PAF-AT, PAF-AH and Lp-PLA(2) activities in 106 healthy volunteers. Men had lower PAF levels and higher activity of both catabolic enzymes and lyso-PAF-AT than women (P-values <0.05). Age was inversely correlated with PAF levels in men (r=-0.279, P=0.06) and lyso-PAF-AT in women (r=-0.280, P=0.05). In contrast, Lp-PLA(2) was positively correlated with age (r=0.201, P=0.04). Moreover, PAF-CPT was positively correlated with glucose (r=0.430, P=0.002) in women. In addition, Principal Component Analysis revealed three PAF metabolic patterns: (i) increased activities of PAF-CPT and PAF-AH, (ii) increased activities of PAF-CPT and lyso-PAF-AT and (iii) increased activity of Lp-PLA(2). The present study underlines the complexity of PAF's metabolism determinants.

Carotid intima media thickness is associated with plasma lipoprotein-associated phospholipase A2 mass in nondiabetic subjects but not in patients with type 2 diabetes

BACKGROUND

A recent meta-analysis showed that both plasma lipoprotein-associated phospholipase A(2) (Lp-PLA(2) ) mass and activity independently predict cardiovascular events. Notably, Lp-PLA(2) activity but not mass was found to be a determinant of cardiovascular outcome in type 2 diabetes mellitus. We questioned whether relationships of carotid intima media thickness (IMT), a measure of subclinical atherosclerosis, with Lp-PLA(2) mass differ between diabetic and nondiabetic subjects.

MATERIALS AND METHODS

Relationships of IMT with plasma Lp-PLA(2) mass (turbidimetric immunoassay) were compared in 74 patients with type 2 diabetes and in 64 nondiabetic subjects.

RESULTS

IMT was increased (P=0·016), but plasma Lp-PLA(2) mass was decreased in patients with diabetes compared to nondiabetic subjects (277±66 vs. 327±62μgL(-1) , P<0·001). In nondiabetic subjects, IMT was correlated positively with Lp-PLA(2) (r=0·325, P<0·009); multiple linear regression analysis confirmed an independent association of IMT with Lp-PLA(2) (ß=0·192, P=0·048). In contrast, IMT was unrelated to Lp-PLA(2) in patients with diabetes (r=0·021, P=0·86), and the relationship of IMT with Lp-PLA(2) was different in diabetic and control subjects (P<0·001). The relationship of Lp-PLA(2) with the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio also differed between diabetic and nondiabetic subjects (P<0·001).

CONCLUSIONS

Plasma Lp-PLA(2) may relate to early stages of atherosclerosis development. In diabetes mellitus, in contrast, the association of IMT with plasma Lp-PLA(2) mass is abolished, which could be partly ascribed to redistribution of Lp-PLA(2) mass from apolipoprotein B-containing lipoproteins towards HDL. These findings raise questions about the usefulness of plasma Lp-PLA(2) mass measurement as a marker of subclinical atherosclerosis in type 2 diabetes mellitus.

Plasma PAF-acetylhydrolase activity, inflammatory markers and susceptibility of LDL to in vitro oxidation in patients with type 1 diabetes mellitus

AIMS

We evaluated if type 1 diabetic patients have altered levels of low-grade inflammatory markers including platelet-activating factor acetylhydrolase (PAF-AH) activity, high-sensitivity C-reactive protein (hs-CRP), white blood cells count (WBC), erythrocyte sedimentation rate (ESR) and LDL-cholesterol oxidation coefficient (OxC), and whether their levels are related to clinical complications and the metabolic profile.

METHODS

We studied cross-sectionally 118 outpatients with type 1 diabetes both with (n=38) and without (n=80) clinical chronic complications, and 110 controls subjects.

RESULTS

Diabetic patients had higher levels of PAF-AH activity (p=0.02), hs-CRP (p=0.001), WBC (p=0.004) and ESR (p=0.0001) than controls. Patients with type 1 diabetes had earlier OxC than the non-diabetic subjects at 1 and 3 h (p=0.01) after the addition of CuSO(4). No difference was noted between patients with and without chronic complications. In the patients, correlations were found between PAF-AH activity and OxC at 1 and 3 h.

CONCLUSIONS

It was concluded that the susceptibility of LDL to in vitro oxidation and low-grade inflammation are increased in patients with type 1 diabetes and related to each other. The presence of these markers is probably independent of the presence of chronic clinical complications and reveals the development of early pro-inflammatory state.