Homocysteinethiolactone and Paraoxonase: Novel markers of diabetic retinopathy

• Published in: Diabetes care Vol. 33; no. 9; pp. 2031 - 2037
• Main Authors: Barathi, Subramaniam, Angayarkanni, Narayanasamy, Pasupathi, Aarthi, Natarajan, Sulochana Konerirajapuram, Pukraj, Rishi, Dhupper, Maneesh, Velpandian, Thirumurthy, Muralidharan, Charanya, Sivashanmugham, Muthukumaran
• Format: Journal Article
• Language: English
• Published: Alexandria, VA American Diabetes Association 01.09.2010
• Subjects: Acids; Aged; analogs & derivatives; Aryldialkylphosphatase; Aryldialkylphosphatase - metabolism; Bioinformatics; Biological and medical sciences; Cells, Cultured; Chromatography, High Pressure Liquid; Crystal structure; Diabetes. Impaired glucose tolerance; Diabetic retinopathy; Diabetic Retinopathy - diagnosis; Diabetic Retinopathy - enzymology; Diabetic Retinopathy - metabolism; diagnosis; Drug therapy; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; endothelial cells; enzymology; Etiopathogenesis. Screening. Investigations. Target tissue resistance; Female; gene expression; Health aspects; Homocysteine; Homocysteine - analogs & derivatives; Homocysteine - metabolism; Human subjects; Humans; in vitro studies; low density lipoprotein; Low density lipoproteins; Male; mass spectrometry; Medical sciences; messenger RNA; Metabolic diseases; metabolism; Middle Aged; Miscellaneous; Original Research; oxidation; patients; protective effect; Proteins; Public health. Hygiene; Public health. Hygiene-occupational medicine; Retinal Perforations; Retinal Perforations - metabolism; reverse transcriptase polymerase chain reaction; Risk factors; Tandem Mass Spectrometry; Vitreous Body; Vitreous Body - metabolism; Endocrinopathy; Human; Retinopathy; Nutrition; Enzyme; Diabetes mellitus; Biological marker; Metabolic diseases; Esterases; Phosphoric triester hydrolases; Eye disease; Hydrolases; Aryldialkylphosphatase; Endocrinology
• ISSN: 0149-5992; 1935-5548; 1935-5548
• DOI: 10.2337/dc10-0132

OBJECTIVE: Paraoxonase (PON) exhibits esterase activity (PON-AREase) and lactonase activity (PON-HCTLase), which prevent LDL oxidation and detoxify homocysteine thiolactone (HCTL). The role of HCTL and PON-HCTLase as a risk factor for the microvascular complication in diabetic retinopathy at the level of vitreous has not been investigated. RESEARCH DESIGN AND METHODS: Undiluted vitreous from patients with proliferative diabetic retinopathy (PDR) (n = 13) and macular hole (MH) (n = 8) was used to determine PON-HCTLase and PON-AREase activity spectrophotometrically. HCTL levels were detected by liquid chromatography-tandem mass spectrometry. In vitro studies were done in primary cultures of bovine retinal capillary endothelial cells (BRECs) to determine the dose- and time-dependent effect of HCTL and homocysteine (Hcys) on PON-HCTLase activity, as well as to determine mRNA expression of PON by RT-PCR. RESULTS: A significant increase in HCTL and PON-HCTLase activity was observed in PDR compared with MH (P = 0.036, P = 0.001), with a significant positive correlation between them (r = 0.77, P = 0.03). The in vitro studies on BRECs showed a dose- and time-dependent increase in the PON-HCTLase activity and mRNA expression of PON2 when exposed to HCTL and Hcys. CONCLUSIONS: This is the first study showing elevated levels of vitreous HCTL and PON-HCTLase activity in PDR. These elevations are probably a protective effect to eliminate HCTL, which mediates endothelial cell dysfunction. Thus, vitreous levels of HCTL and PON activity can be markers of diabetic retinopathy. The bioinformatics analysis reveals that the structure and function of PON that can be modulated by hyperhomocysteinemia in PDR can affect the dual-enzyme activity of PON.