Abstract
Summary Background: Increased levels of lipoprotein-associated phospholipase A2 are associated with atherosclerosis, and may contribute to cardiac disease. The aim of this study was to analyze serum levels of lipoprotein phospholipase A2 (Lp-PLA2) in patients with impaired bone resorption and correlate the findings with markers of bone metabolism (osteocalcin) and other biochemical markers (cholesterol, low density lipoprotein, triacylglycerols). Methods: Serum Lp-PLA2 was measured by a turbidimetric method in a group of currently treated 85 patients with impaired bone resorption and in a control group of 46 healthy individuals. Serum triacylglycerols was measured by the electrochemiluminescence immunoassay. Cholesterol, low density lipoprotein and triacylglycerols were measured by commercially available enzymatic assays. Bone density was investigated by dual energy X-ray densitometry performed on the lower spine and hips. Results: Concentrations of LP-PLA2 were significantly elevated in the patients with bone resorption compared to the control group of healthy individuals (225 ng/mL vs. 192 ng/mL, p>0.001) with the highest difference in patients with a T score below –2.5 SD (227 vs. 192 ng/mL). Serum levels of Lp-PLA2 also negatively correlated with decreased levels of serum osteocalcin in patients, and a significant difference in Lp-PLA2 (p=0.02) levels was observed between the control group and group with low levels of osteocalcin. Elevated Lp-PLA2 levels were significantly associated with the therapeutic procedures used, but not with age, gender and concentration of lipids. Conclusions: Lipoprotein-associated phospholipase A2 seems to play an important role also in bone metabolism.
Highlights
Lipoprotein-associated phospholipase A2 (LpPLA2) is a circulating enzyme belonging to the unrelated phospholipase A2 protein families with common enzymatic activity
Serum levels of lipoprotein phospholipase A2 (Lp-PLA2) were measured in the control group of healthy individuals and in the whole group of patients
The median Lp-PLA2 value in patients was significantly elevated in comparison with healthy individuals (225 ng/mL vs. 192 ng/mL, p
Summary
Lipoprotein-associated phospholipase A2 (LpPLA2) is a circulating enzyme belonging to the unrelated phospholipase A2 protein families with common enzymatic activity. The two most notable families are secreted phospholipases A2 and cytosolic phospholipases A2. Other families include Ca2+ independent PLA2 (iPLA2) and lipoprotein-associated PLA2, known as platelet activating factor acetylhydrolase (PAF-AH). Recent evidence has established physiological and pathological roles of PLA2 enzymes in fertility, muscle growth, renal concentration, postischemic brain injury, inflammatory and oxidative activities associated with cardiovascular disease and ischemic stroke, inflammatory bone resorption, intestinal polyposis, pulmonary fibrosis, acute respiratory distress syndrome and autoimmune encephalomyelitis [1]. Cytosolic phospholipases preferentially hydrolyze phospholipids containing arachidonic acid and play a key role in the biosynthesis of eicosanoids including prostaglandins and leucotrienes [2]. Prostaglandin (especially prostaglandin E2) is produced by osteoblasts and acts as a potent stimulator of bone resorption [1, 3]
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