Unexpected inverse relationship between impaired glucose metabolism and lipoprotein-associated phospholipase A2 activity in patients with stable vascular disease

Mediation of Systemic Inflammation on Insulin Resistance and Prognosis of Nondiabetic Patients With Ischemic Stroke

BACKGROUND

Insulin resistance is associated with stroke recurrence and poor functional outcomes of nondiabetic patients with ischemic stroke. The study aimed to investigate whether the association between insulin resistance and the prognosis of nondiabetic patients with ischemic stroke was mediated by systematic inflammation.

METHODS

Patients with ischemic stroke but without a history of diabetes who were enrolled in CNSR-III (Third China National Stroke Registry) were included in the study and followed up for 1 year after stroke onset. Insulin resistance was determined by using the homeostasis model assessment for insulin resistance (HOMA-IR) method. hs-CRP (high-sensitivity C-reactive protein) and Lp-PLA₂ (lipoprotein-associated phospholipase A₂) activity were measured at baseline. The primary outcome was stroke recurrence, and other outcomes included composite vascular events, mortality, and poor functional outcome (modified Rankin Scale score, 3-6). Multivariable Cox or logistic regression analyses were performed to estimate the association between HOMA-IR and the study outcomes. A mediation analysis was performed to examine the relationship between insulin resistance and the study outcomes mediated by systemic inflammation.

RESULTS

Among a total of 3808 nondiabetic patients with ischemic stroke who were included in the study, the median HOMA-IR was 1.79 (interquartile range, 1.05-2.97). After adjustments for potential confounders, higher HOMA-IR quartiles were associated with higher risks of stroke recurrence, ischemic stroke, and composite vascular events, especially in the large artery atherosclerosis subtype. hs-CRP partially mediated the association between the HOMA-IR index and the prognosis of ischemic stroke (mediation proportion, 5.9% for stroke recurrence and 7.5% for composite vascular events). No evidence of Lp-PLA₂ activity mediating the association of insulin resistance with stroke outcomes was observed.

CONCLUSIONS

Our study found that insulin resistance was associated with poor clinical outcomes in nondiabetic patients with ischemic stroke, which was partially mediated by hs-CRP with a modest amount.

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.

Lipoprotein-associated phospholipase A₂ activity is increased in patients with definite familial hypercholesterolemia compared with other forms of hypercholesterolemia

BACKGROUND AND AIM

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) plays a key role in atherosclerosis development. It is considered a marker of increased risk of cardiovascular disease (CVD) and plaque vulnerability. Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated plasma levels of low-density lipoprotein cholesterol and a higher prevalence of early CVD. Our aim was to evaluate the differences in Lp-PLA₂ activity in a population of hypercholesterolemic patients with and without definite FH.

METHODS AND RESULTS

Hypercholesterolemic patients were consecutively recruited. Definite FH was defined according to Dutch Lipid Clinic Network criteria ≥8. All patients underwent routine clinical examination and biological assessments and Lp-PLA₂ activity was measured in blood samples. Among 469 patients, 118 had a definite diagnosis of FH. Lp-PLA₂ activity was significantly higher in definite FH patients compared to non-definite FH patients (206.5 ± 54.5 vs. 180.8 ± 48.4 nmol/min/mL, p < 0.0001). Lp-PLA₂ positively correlated with total cholesterol, LDL-C and apolipoprotein B and negatively with HDL-C and apolipoprotein A-1. In multivariate analysis, definite FH diagnosis, LDL-C, HDL-C and statin treatment remained correlates of Lp-PLA₂ independently of systolic blood pressure.

CONCLUSIONS

Lp-PLA₂ activity was higher in definite FH than in non-definite FH patients independently of LDL-C levels and statin treatment. These results highlight the particular phenotype of FH subjects among hypercholesterolemic patients. As increased Lp-PLA₂ activity suggests, FH patients exhibit higher arterial inflammation that may contribute to their high cardiovascular risk. Our results reinforce the potential beneficial role of statins pleiotropic effects and the need for proper identification and treatment of FH patients.

Lipoprotein-associated phospholipase A2 activity in obese adolescents with and without type 2 diabetes

Lipoprotein-associated phospholipase A2 (Lp-PLA2) was identified as a strong predictor for cardiovascular events. Furthermore, it is highly associated with obesity. The role of Lp-PLA2 in diabetes mellitus is controversial and analyses, especially in adolescents with type 2 diabetes (T2D), are missing. Therefore, we compared Lp-PLA2 activity between two obese age-, sex-, and BMI-matched cohorts of adolescents with and without T2D. Relationships between Lp-PLA2 activity and age, BMI, hemoglobin A1c, lipids, and adipokines were evaluated. Lp-PLA2 activity was analyzed in serum of 72 obese adolescents without T2D (mean age 15.2 ± 1.6 years) and in 65 obese adolescents with T2D (mean age 15.5 ± 1.8 years). Clinical data were obtained from the Diabetes-Patienten-Verlaufsdokumentation (DPV) registry. Surprisingly, obese adolescents with T2D had lower levels of Lp-PLA2 activity than obese children without T2D (160.2 ± 45.0 versus 180.9 ± 35.6 nmol/min/ml, p = 0.003), but this decrease could only be detected in male (158.8 ± 45.3 versus 190.8 ± 31.3 nmol/min/ml, p < 0.001) and not in female adolescents (162.1 ± 45.5 versus 167.7 ± 37.1 nmol/min/ml, p = 0.60). In multiple linear regression analysis, differences in Lp-PLA2 activity between cohorts remained large and significant (ß-coefficient: -31.60, 95% confidence interval [-49.27;-13.93], p < 0.001). Furthermore, Lp-PLA2 activity was positively associated with BMI (ß-coefficient: 2.04 [0.68;3.40], p = 0.004) and negatively associated with the adipokines leptin (ß-coefficient: -0.53 [-0.89;-0.17], p = 0.004) and adiponectin (ß-coefficient: -3.06, [-5.63;-0.48], p = 0.02). Elevated mean glucose concentrations in adolescents with T2D were not associated with an increase but with a decrease of Lp-PLA2 activity. Hence, in young patients with T2D the Lp-PLA2 activity as a risk predictor for cardiovascular events needs further investigation.

Maternal Gestational Diabetes Mellitus increases placental and foetal lipoprotein-associated Phospholipase A2 which might exert protective functions against oxidative stress

Increased Lipoprotein associated phospholipase A2 (LpPLA2) has been associated with inflammatory pathologies, including Type 2 Diabetes. Studies on LpPLA2 and Gestational Diabetes Mellitus (GDM) are rare, and have focused mostly on maternal outcome. In the present study, we investigated whether LpPLA2 activity on foetal lipoproteins is altered by maternal GDM and/or obesity (a major risk factor for GDM), thereby contributing to changes in lipoprotein functionality. We identified HDL as the major carrier of LpPLA2 activity in the foetus, which is in contrast to adults. We observed marked expression of LpPLA2 in placental macrophages (Hofbauer cells; HBCs) and found that LpPLA2 activity in these cells was increased by insulin, leptin, and pro-inflammatory cytokines. These regulators were also increased in plasma of children born from GDM pregnancies. Our results suggest that insulin, leptin, and pro-inflammatory cytokines are positive regulators of LpPLA2 activity in the foeto-placental unit. Of particular interest, functional assays using a specific LpPLA2 inhibitor suggest that high-density lipoprotein (HDL)-associated LpPLA2 exerts anti-oxidative, athero-protective functions on placental endothelium and foetus. Our results therefore raise the possibility that foetal HDL-associated LpPLA2 might act as an anti-inflammatory enzyme improving vascular barrier function.

Effect of intensive insulin treatment on plasma levels of lipoprotein-associated phospholipase A2 and secretory phospholipase A2 in patients with newly diagnosed type 2 diabetes

Background

China has the highest absolute disease burden of diabetes worldwide. For diabetic patients, diabetes-related vascular complications are major causes of morbidity and mortality. The roles of lipoprotein-associated phospholipase A₂ (Lp-PLA₂) and secretory phospholipase A₂ (sPLA₂) as inflammatory markers have been recently evaluated in the pathogenesis of both diabetes and atherosclerosis. We aimed to determine the mechanism through which patients with newly diagnosed type 2 diabetes gain long-term vascular benefit from intensive insulin therapy by evaluating the change in Lp-PLA₂ and sPLA₂ levels after early intensive insulin treatment and its relevance with insulin resistance and pancreatic β-cell function.

Methods

In total, 90 patients with newly diagnosed type 2 diabetes mellitus were enrolled. All patients received continuous subcutaneous insulin infusion (CSII) for approximately 2 weeks. Intravenous glucose-tolerance test (IVGTT) and oral glucose-tolerance test (OGTT) were performed, and plasma concentrations of Lp-PLA₂ and sPLA₂ were measured before and after CSII.

Results

Levels of Lp-PLA₂ and sPLA₂ were significantly higher in diabetic patients with macroangiopathy than in those without (P < 0.05). After CSII, the sPLA₂ level decreased significantly in all diabetic patients (P < 0.05), while the Lp-PLA2 level changed only in those with macroangiopathy (P < 0.05). The area under the curve of insulin in IVGTT and OGTT, the acute insulin response (AIR_3–5), early phase of insulin secretion (ΔIns30/ΔG30), modified β-cell function index, and homeostatic model assessment for β-cell function (HOMA-β) increased after treatment even when adjusted for the influence of insulin resistance (IR; P < 0.001). The HOMA-IR was lower after treatment, and the three other indicators adopted to estimate insulin sensitivity (ISI_ced, IAI, and QUICKI) were higher after treatment (P < 0.05). Correlation analysis showed that the decrease in the Lp-PLA₂ and sPLA₂ levels was positively correlated with a reduction in HOMA-IR after CSII (P < 0.05). Additionally, multiple linear regression analysis showed that Lp-PLA₂ and sPLA₂ independently correlated with HOMA-IR (P < 0.05).

Conclusions

Lp-PLA₂ and sPLA₂ are closely related to insulin resistance and macroangiopathy in diabetic patients. Intensive insulin therapy might help improve IR and protect against diabetic macroangiopathy by influencing the Lp-PLA₂ and sPLA₂ levels.

Trial registration

ChiCTR-TRC-10001618 2010 September 16.

Emerging Cardiovascular Disease Biomarkers and Incident Diabetes Mellitus Risk in Statin-Treated Patients With Coronary Artery Disease (from the Treating to New Targets [TNT] Study)

Whether biomarkers associated with cardiovascular disease risk also predict incident diabetes mellitus (DM) is unknown. Our objective was to determine if a panel of 18 biomarkers previously associated with risk of cardiovascular disease also predicts incident DM in statin-treated patients with coronary artery disease (CAD). The Treating to New Targets (TNT) study is a randomized trial that compared the efficacy of high (80 mg) versus low (10 mg) dose atorvastatin for the secondary prevention of coronary heart disease events. Fasting plasma levels of standard lipids and of 18 emerging CAD risk biomarkers were obtained after an 8-week run-in period on atorvastatin 10 mg in a random sample of 1,424 TNT patients. After exclusion of patients with DM at baseline (n = 253), 101 patients developed DM during the median follow-up of 4.9 years. Patients with incident DM had lower levels of total and high-molecular weight adiponectin, lipoprotein-associated phospholipase A2 (Lp-PLA2), soluble receptor of advanced glycation end products, and vitamin D compared with patients without incident DM. In contrast, insulin, soluble CD40 ligand, and soluble intercellular adhesion molecule-1 levels were higher in patients with incident DM compared with those without. Plasma levels of C-reactive protein, cystatin C, lipoprotein(a), monocyte chemotactic protein-1, matrix metalloproteinase-9, myeloperoxidase, neopterin, N-terminal fragment of pro-B-type natriuretic peptide, osteopontin, and soluble vascular cell adhesion molecule-1 were comparable in patients with and without incident DM. After multivariate adjustment, total and high-molecular weight adiponectin as well as Lp-PLA2 were negatively associated with incident DM. Results of this study suggest that plasma lipids and some emerging CAD risk biomarkers, such as adiponectin and Lp-PLA2, may be useful for predicting incident DM in statin-treated patients with stable CAD.

Lipoprotein-Associated Phospholipase A2 Activity Is a Marker of Risk But Not a Useful Target for Treatment in Patients With Stable Coronary Heart Disease

BACKGROUND

We evaluated lipoprotein-associated phospholipase A2 (Lp-PLA2) activity in patients with stable coronary heart disease before and during treatment with darapladib, a selective Lp-PLA2 inhibitor, in relation to outcomes and the effects of darapladib in the STABILITY trial.

METHODS AND RESULTS

Plasma Lp-PLA2 activity was determined at baseline (n=14 500); at 1 month (n=13 709); serially (n=100) at 3, 6, and 18 months; and at the end of treatment. Adjusted Cox regression models evaluated associations between Lp-PLA2 activity levels and outcomes. At baseline, the median Lp-PLA2 level was 172.4 μmol/min per liter (interquartile range 143.1-204.2 μmol/min per liter). Comparing the highest and lowest Lp-PLA2 quartile groups, the hazard ratios were 1.50 (95% CI 1.23-1.82) for the primary composite end point (cardiovascular death, myocardial infarction, or stroke), 1.95 (95% CI 1.29-2.93) for hospitalization for heart failure, 1.42 (1.07-1.89) for cardiovascular death, and 1.37 (1.03-1.81) for myocardial infarction after adjustment for baseline characteristics, standard laboratory variables, and other prognostic biomarkers. Treatment with darapladib led to a ≈65% persistent reduction in median Lp-PLA2 activity. There were no associations between on-treatment Lp-PLA2 activity or changes of Lp-PLA2 activity and outcomes, and there were no significant interactions between baseline and on-treatment Lp-PLA2 activity or changes in Lp-PLA2 activity levels and the effects of darapladib on outcomes.

CONCLUSIONS

Although high Lp-PLA2 activity was associated with increased risk of cardiovascular events, pharmacological lowering of Lp-PLA2 activity by ≈65% did not significantly reduce cardiovascular events in patients with stable coronary heart disease, regardless of the baseline level or the magnitude of change of Lp-PLA2 activity.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00799903.