Abstract
To characterize the role of interleukin-6 (IL-6) in estrogen (E 2)-depletion bone loss, we utilized a nonhuman primate model of human skeletal physiology. Adult female rhesus monkeys were sham-operated (S; n = 5), ovariectomized (ovx; n = 10), or ovx followed by E 2 replacement (ovx + E 2; n = 10) and evaluated for the indicated parameters at 0, 3, 6, and 9 months post-ovx. Lumbar spine bone mineral density (BMD) decreased by 3 months and continued to decline through 9 months in the ovx, but not in the ovx + E 2 or S groups. Middle and distal radius BMD was decreased at 9 months in the ovx, but not in the ovx + E 2 or S groups. The S group had marked fluctuations in bone remodeling parameters, and cytokine levels in S animals were consistent with menstrual cycling, and therefore only those values in the ovx and ovx + E 2 groups are reported. Serum osteocalcin and skeletal-specific alkaline phosphatase were elevated in the ovx group compared with the ovx + E 2 group. There was no difference in serum or bone marrow plasma IL-6 levels between the ovx and ovx + E 2 groups. Similarly, there was no difference in basal or phorbol ester-stimulated IL-6 levels of peripheral blood mononuclear cell or bone marrow cell culture supernatants between groups. There was no difference in serum or bone marrow soluble IL-6 receptor between groups. However, the bone marrow plasma soluble IL-6 receptor levels were transiently increased from baseline at 3 months in the ovx but not in the ovx + E 2 group. In summary, there was no bone loss in the ovx + E 2 group, although the serum and bone marrow IL-6 levels were similar to those of the ovx group. These data suggest that modulation of IL-6 is not the key mechanism through which estrogen deprivation mediates bone loss in rhesus monkeys.
Published Version
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