Relations of lysophosphatidylcholine in low-density lipoprotein with serum lipoprotein-associated phospholipase A 2, paraoxonase and homocysteine thiolactonase activities in patients with type 2 diabetes mellitus

Abstract

Aims We studied the relations of lysophosphatidylcholine (lyso-PC) in LDL with serum lipoprotein-associated phospholipase A 2 (Lp-PLA 2), paraoxonase and homocysteine thiolactonase (HTLase) activities in patients with type 2 diabetes mellitus. Methods Lyso-PC was measured by electrospray ionization-liquid chromatography/mass spectrometry. Paraoxonase and HTLase activities were measured with paraoxon and γ-thiobutyrolactone as substrates, respectively. Results Serum HTLase and paraoxonase activities were significantly suppressed in diabetic patients ( n = 96) compared with control ( n = 25), whereas serum Lp-PLA 2 did not differ in control and diabetic patients. Lyso-PC contents in LDL correlated with serum Lp-PLA 2 activity positively and with serum HTLase activity negatively. Stepwise regression analysis revealed that serum Lp-PLA 2 and HTLase activities independently contributed to lyso-PC contents in LDL. In patients with diabetic nephropathy, lyso-PC contents in LDL were increased with reduced serum HTLase and paraoxonase activities compared with control, while serum Lp-PLA 2 activity did not differ. On the other hand, 3-month treatment with simvastatin reduced both lyso-PC contents in LDL and serum Lp-PLA 2 activity in hypercholesterolemic diabetic patients, while serum HTLase or paraoxonase activities did not change. Conclusions Increased lyso-PC contents in LDL were associated with the suppressed HTLase activity, and serum Lp-PLA 2 and HTLase activities may be related to lyso-PC in type 2 diabetic patients.