ABSTRACT
The purpose of the study was to determine the effects of exercise-associated menstrual disorders and hormonal contraceptives (HC) on systemic inflammatory markers and endothelial function in female athletes. Thirty-nine active women (≥5 h of aerobic exercise per wk), aged 18-33 y, participated in this cross-sectional study comparing women with menstrual disorders (MD, n = 10; 0-9 cycles·y(-1)), eumenorrheic women (E, n = 13; 10-13 cycles·y(-1)), and HC users (HC, n = 16; 12 cycles·y(-1)). Fasting serum samples were collected during the early follicular phase (d2-5) for the menstruating women. Tumor necrosis factor-α (TNFα), interleukin-6 (IL-6), C-reactive protein (CRP), soluble vascular adhesion molecule-1 (sVCAM-1), total cholesterol (TC), high- and low density lipoprotein-cholesterol (HDL-C, LDL-C), triglycerides (TG), reproductive hormones, and cortisol were measured in serum. Estradiol, progesterone, and cortisol were not statistically different between MD and E groups; cortisol was significantly greater in the HC versus E group (p = 0.002). TC (p = 0.005), LDL-C (p = 0.03), and CRP (p = 0.05) were increased in the HC versus MD and E groups. TNF-α was significantly higher in the HC (p=0.001) compared with the E group. There were no significant group differences in the concentrations of sVCAM-1 or IL-6. TNF-α and cortisol were positively correlated (r=0.31, p = 0. 058), as were sVCAM-1 and estradiol (r = 0.41, p = 0.010). In conclusion, HC use, but not exercise- associated menstrual disorders, is associated with increased TNFα and LDL-C. Key PointsSerum lipids and markers of inflammation were not altered by exercise-associated oligomenorrhea or amenorrhea.Hormonal contraceptive users had elevated total and LDL cholesterol compared with regularly menstruating non-HC users.C-reactive protein and tumor necrosis factor-α, but not soluble vascular adhesion molecule-1, were increased in hormonal contraceptive users.The long-term effect of these changes on cardiovascular disease is unknown.
ABSTRACT
Urate oxidase catalyzes the oxidation of urate without the involvement of any cofactors. The gene encoding urate oxidase from Bacillus subtilis has been cloned and expressed, and the enzyme was purified and characterized. Formation of the urate dianion is believed to be a key step in the oxidative reaction. Rapid-mixing chemical quench studies provide evidence that the dianion is indeed an intermediate; at 15 degrees C the dianion forms within the mixing time of the rapid-quench instrument, and it disappears with a rate constant of 8 s(-)(1). Steady-state kinetic studies indicate that an ionizable group on the enzyme with a pK of 6.4 must be unprotonated for catalysis, and it is presumed that the role of this group is to abstract a proton from the substrate. Surprisingly, examination of the active site provided by the previously reported crystal structure does not reveal any obvious candidates to act as the general base. However, Thr 69 is hydrogen-bonded to the ligand at the active site, and Lys 9, which does not contact the ligand, is hydrogen-bonded to Thr 69. The T69A mutant enzyme has a V(max) that is 3% of wild type, and the K9M mutant enzyme has a V(max) that is 0.4% of wild type. The ionization at pH 6.4 that is observed with wild-type enzyme is absent in both of these mutants. It is proposed that these residues form a catalytic diad in which K9 deprotonates T69 to allow it to abstract the proton from the N9 position of the substrate to generate the dianion.
