Effect of insulin on the incorporation of citrate and calcium into the bones of alloxan-diabetic rats

Summary

Diabetes results in osteoporosis, which is characterized by a loss of bone calcium, and thinness of bone shaft. Bone is a major reservoir of calcium and citrate in the body. In this report the effect of diabetes on the deposition of calcium and citrate into rat bones is studied.

When [1-5-¹⁴C]citrate (50µCi/kg body wt.) was injected intravenously, the bones of untreated alloxan-diabetic rats incorporated less labeled citrate than those of insulin-treated diabetic or control animals. Likewise, when [1-¹⁴C]acetate was injected (50µCi/kg body wt.), the labeled citrate synthesized in vivo was incorporated into untreated diabetic rat bones to a significantly lesser extent than in those of insulin-treated diabetic or control rats. In these in vivo studies citrate oxidation was minimized by administration of either an i.v. injection of monofluoroacetic acid (10 mg/kg body wt.) or an i.p. dose of trans-aconitate (2 g/kg body wt.) prior to the administration of labeled acetate or citrate.

When⁴⁵Ca (100µCi/kg body wt.) was injected subcutaneously for 2 consecutive days, the bones of diabetic rats deposited markedly less of the isotope than those of insulin-treated diabetic or control animals.

It is concluded that decreased bone mass in diabetes may be a consequence of decreased calcium deposition in the bone.