Results: Oxidative stress predicts hip fracture in postmenopausal women -
Oxidative stress is a significant predictor of hip fracture in postmenopausal women, according a new study by the University of Cincinnati (UC) epidemiologists.
research, appearing online ahead of print in the Journal of Bone and Mineral Research , was directed by Tianying Wu, MD, PhD, assistant professor at the UC College of Department medicine environmental health and Shuman Yang, a postdoctoral fellow in the department. They collaborated with researchers from the Harvard School of Public Health and Harvard Medical School.
"To our knowledge, this is the first prospective study among postmenopausal women showing that oxidative stress was a significant predictor for hip fracture," said Wu, the corresponding author of the study.
Oxidative stress is defined as a physiological stress on the body that is caused by the cumulative damage caused by free radicals, which are not sufficiently neutralized by antioxidants. The free radicals are unstable molecules which react with other substances in the human body to cause damage to cells or organs.
Oxidative stress occurs naturally, but environmental factors such as natural and artificial radiation, toxins in the air, food and water and various sources such as tobacco smoke can add the overall charge and defeat the antioxidant defenses of the body.
researchers assessed oxidative stress by measuring fluorescent oxidation products (FLOP) in blood plasma. FLOP reflects a mixture of oxidation products of lipids, proteins and DNA and can be measured by a fluorescent spectrophotometer.
The researchers studied participants in the health study of nurses that began in 1976 with funding from the National Institutes of Health (NIH). Participants are nurses who regularly respond to questionnaires and submit samples.
The researchers studied 996 women aged 60 or over to the collection of baseline blood (1989-190). FLOPS plasma were measured at three wavelength excitation / emission: 360/420 nm (nanometers), named FlOP_360; 320/420 nm, named as FlOP_320; and 400-475 nm, named FlOP_400.
FlOP_360 represents the oxidation products which are generated from oxidized phospholipids or oxidation products of lipids reactive with proteins. FlOP_320 is formed when the products of oxidation such as lipid hydroperoxides, aldehydes and ketones react with DNA in the presence of metals. FlOP_400 reflects the interaction between the malondialdehyde (a marker specific for the oxidation of lipids), proteins and phospholipids.
Of the three wavelengths, the researchers found that FlOP_320 products baseline predicts future risk of hip fracture in the study cohort. (No association was found with FlOP_360 and FlOP_400.) Increase FlOP_320 was associated with an increased risk of hip fracture; women in the top 30 percent of FlOP_320 readings were found to have 2.67 times the risk of hip fractures from those in the bottom of 30 percent.
"Because FlOP_320 is generated in the presence of metals, its strong association with hip fractures may reflect co-existing effect of reactive oxygen species and heavy metals," said Wu which notes that other FLOP products can be generated without metals.
Hip fracture is associated with a substantial cost, and a higher risk of disability, comorbidities and mortality than other fractures. Fracture risk assessment current uses traditional risk factors such as age and the presence of osteoporosis, but Wu sees FlOP_320 play an important role in the risk assessment.
"If our results are confirmed by other studies, the addition of this marker in the existing fracture assessment model may improve the prediction of hip fracture in postmenopausal women", they say she.
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