title: Seasonal variation in copper-mediated low-density lipoprotein oxidation in vitro is related to varying plasma concentration of oxidised lipids in summer and winter.
abstract: The seasonal variation of CuCl2-mediated low density lipoprotein (LDL) oxidation (10 microM Cu2+, lag phase, rate of oxidation and maximum absorbance at 234 nm) were measured in 43 men and women on 4-6 occasions (mean 5.7 +/- 0.5) over a 12-month period. The lag phase averaged 52.7 +/- 0.6 min and did not differ by gender. Lag phase and rate of the rapid propagation phase of LDL oxidation showed a sinusoidal pattern over the year (increased and reduced oxidative susceptibility during January and June-July, respectively; both p < 0.001). Changes in plasma alpha-tocopherol, ascorbic acid, lycopene or beta-carotene concentrations did not explain seasonal differences in oxidative susceptibility of LDL in vitro. Nor did plasma lipid content of linoleic acid, the main substrate of lipid peroxidation, vary. However, the amount of hydroperoxy- plus hydroxy-fatty acids in plasma lipids varied according to season (p < 0.024) and was related to the lag phase (r = -0.26, p < 0.001). Seasonal variation in oxidative susceptibility was not significant after adjusting for hydroperoxy- plus hydroxy-fatty acids (p = 0.506). Isolated LDL is more vulnerable to Cu2+-induced lipid peroxidation during the winter and this may be due to the higher amount of oxidised lipids during that period.
authors.affiliation: Cardiovascular Research, University of Edinburgh, George Square, Edinburgh EH8 9XF, UK. rudolph.riemersma@ed.ac.uk
authors.forename: R A
authors.initials: RA
authors.lastname: Riemersma
authors.forename: R
authors.initials: R
authors.lastname: Wilson
authors.forename: J A
authors.initials: JA
authors.lastname: Payne
authors.forename: M J
authors.initials: MJ
authors.lastname: Shepherd
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000097:blood; D002338:Carotenoids / Q000097:blood; D005260:Female; D006801:Humans; D050356:Lipid Metabolism; D015227:Lipid Peroxidation; D008055:Lipids / Q000097:blood; D008077:Lipoproteins, LDL / Q000378:metabolism*; D000077276:Lycopene; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D012621:Seasons; D012737:Sex Factors; D013997:Time Factors; D024502:alpha-Tocopherol / Q000097:blood; D019207:beta Carotene / Q000097:blood
chemical_list: D000975:Antioxidants; D008055:Lipids; D008077:Lipoproteins, LDL; D019207:beta Carotene; D002338:Carotenoids; D024502:alpha-Tocopherol; D001205:Ascorbic Acid; D010100:Oxygen; D000077276:Lycopene