Background: Although vitamin K2 has been shown to prevent prednisolone-induced loss of bone mineral density of the lumbar spine in patients with chronic glomerulonephritis, the magnitude of this effect remains to be clarified. The aim of this prospective study is to compare the protective effect of vitamin K2 with that of vitamin D3 on prednisolone-induced loss of bone mineral density in patients with chronic glomerulonephritis.
Methods: Sixty patients (28 men, 32 women) were randomly divided into 4 groups (n = 15 each group): control (group C), vitamin D3 alone (alfacalcidol, 0.5 microg/d; group D), vitamin K2 alone (menatetrenone, 45 mg/d; group K), and vitamins D3 plus K2 (group D + K). Alfacalcidol and menatetrenone therapy were started at the same time as prednisolone. Bone mineral density of the lumbar spine (L2 to L4) was determined by means of dual-energy X-ray absorptiometry, and various biochemical parameters of calcium and bone homeostasis were assessed before and at the end of week 8 of treatment.
Results: Treatment with prednisolone alone caused loss of bone mineral density, which could be fully prevented in groups D, K, and D + K. However, marked reductions in levels of several biochemical markers of both bone formation and resorption also were observed in all groups. The preventive effect in groups K and D + K on loss of bone mineral density induced by prednisolone was similar to that in group D. The elevation in serum calcium levels observed in group D was attenuated in group D + K.
Conclusion: Protective effects of vitamin K2 or vitamins D3 and K2 on prednisolone-induced loss of bone mineral density are similar to that of vitamin D3.