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Nitro-bisphosphonates may inhibit antioxidant vitamin E levels in women with osteoporosis
In postmenopausal women with osteoporosis, treatment with nitro-bisphosphonates appears to be associated with diminished coenzyme Q10 status and vitamin E levels, according to recent study findings.
Researchers for the observational cross-sectional study evaluated 71 postmenopausal women older than 59 years with a diagnosis of age-related osteoporosis. Blood samples were collected, processed and frozen for 2 to 8 months. Researchers then evaluated the antioxidant status by measuring the plasma levels of antioxidants essential to counteracting oxidative stress. These included ascorbic acid (vitamin C) and the two predominant forms of vitamin E (alpha- and gamma-tocopherol). Measurements of oxidized and decreased forms of coenzyme Q10 were conducted using high-pressure liquid chromatography with electrochemical detection.
The study participants were grouped according to nitro-bisphosphonate (N-BP) use. Of the 71 women, 17 received no N-BP, 27 were on an oral N-BP regimen and 27 were being treated with IV N-BP. The investigators used Spearman-ranked correlation to evaluate links among measures of oxidation, antioxidant status and cellular aging. Additionally, they used multiple linear regression modeling to anticipate levels of gamma-tocopherol with age, coenzyme Q10 and ascorbic acid. Age and duration of N-BP treatment were the main predictive factors used to represent the coenzyme Q10/cholesterol ratio. The study found a significant decrease in vitamin E gamma-tocopherol levels (P<.001). A contrary association was discovered between duration of N-BP treatment and the coenzyme Q10/cholesterol ratio (P=.025). The coenzyme Q10/cholesterol ratio in patients on an IV N-BP regimen was found to be especially low, at or below the lower limit of the 95% reference range of 119 mcmol/mol for white women (P=.02).
Besides its anti-bone resorption mechanism, N-BP may block a pathway that is involved in the cellular synthesis of coenzyme Q10, which in turn may place a greater antioxidant burden on vitamin E, according to the researchers. They added that based on these findings, adjunctive supplementation may be warranted.
“Investigations are now needed to determine whether coenzyme Q10 and vitamin E gamma-tocopherol deficiency are contributing factors for some serious N-BP-associated adverse effects,” the researchers wrote.
Disclosure: The researchers report no relevant financial disclosures.