"Glycated" osteocalcin in human and bovine bone. The effect of age

Purified osteocalcin from cow and calf bone was analyzed for nonenzymatic glycosylation (glycation) by sodium [3H]borohydride reduction. Calf bone was found to be approximately 5% glycated, while bone from mature cows was 10% glycated. These results were confirmed by a second method which utilizes periodate oxidation followed by formaldehyde fluorescence. Osteocalcin in human bone was also found to be glycated. The content of glycated osteocalcin from the bones of 47 nondiabetic individuals, aged 0.6-97, was dependent upon age. The extent of glycation was lowest in children, was constant through the adult years, and increased linearly in bone taken from individuals aged 60-97. Glycated osteocalcin was purified by boronate affinity chromatography and subjected to one-step Edman degradation. It was established that the site of glycation was the amino-terminal tyrosine. Increases in the amount of glycated osteocalcin in the bones of older individuals may play a role in the pathogenesis of senile osteoporosis and in the osteopenia which may accompany diabetes mellitus.