Prospective evaluation of free radicals and antioxidant activity following 6-month risedronate treatment in patients with postmenopausal osteoporosis
Abstract
In addition to the well-described implications
of estrogen deficiency in postmenopausal osteoporosis
(PMO), free radicals are also effective on bone metabolism.
The antioxidant vitamins C and E play an important
role in the production of collagen, mesenchymal cell differentiation
into osteoblasts, and bone mineralization.
Therefore, the incidence of osteoporosis and the risk of
fractures were decreased with vitamin C and E. It was
proposed that free oxygen radicals are responsible for
biological aging, atherosclerosis, carcinogenesis, and
osteoclastic activity via their negative effects on the cell
and DNA. In this study, we aimed to investigate and
compare the levels of free radicals and serum antioxidant
activity in patients with PMO and healthy subjects before
and after six-month treatment with risedronate, which is an
inhibitor of bone resorption. Twenty-three postmenopausal
patients aged between 52–83 (mean [± standard deviation]
67.6 ± 8.17) with T scores below -2.5 in femur neck or
L1-L4, and 23 postmenopausal healthy subjects were
enrolled into the study. Patients who had received any
medications within the last 6 months that could alter bone
metabolism were excluded. Serum malondialdehyde
(MDA), superoxide dismutase (SOD), and glutathione
peroxidase (GPx) levels were analyzed in both groups. The
patients with PMO were commenced on 5 mg of risedronate,
1,200 mg of calcium, and 800 IU of vitamin D daily.
The patients were reevaluated at the end of the sixth month.
MDA and SOD levels were similar in patients with PMO
when compared to the healthy group before the treatment,
while the GPx levels were lower in patients with PMO
(P = 0.014). GPx (P = 0.028) and MDA (P = 0.04) levels
were increased in patients with PMO after the treatment.
In contrast, SOD levels were decreased when
compared to the initial levels (P = 0.006). There may be
an insufficiency in different steps of the enzymatic antioxidant
systems in patients with PMO without treatment.
We observed an increment in lipid peroxidation levels and
GPx levels with risedronate. We think that the decrement
in SOD levels may be related with the utilized antioxidants
due to the increased free radicals and the compensatory
increment in the other steps of the antioxidant system.