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Sex- and age-related changes in bone and serum osteocalcin

SummaryWe measured bone osteocalcin concentrations in EDTA extracts from iliac crest cortical bone specimens obtained postmortem from 63 men and 71 women (age range 19–90 years), and serum osteocalcin levels in healthy blood donors, 49 men and 49 women (age range 21–65 years). Bone and serum osteocalcin concentrations were higher in men than in women, and an age-related decline was observed in both sexes. In women, however, a temporary increase in serum (P<0.05) osteocalcin was seen in the sixth decade. This study shows sex- and age-related changes in bone osteocalcin consistent with changes in serum osteocalcin, confirming that serum measurement of osteocalcin reflects bone levels. As osteocalcin reflects osteoblastic activity and thus bone formation, the overall decline in bone and serum osteocalcin in men and women, and the increase in serum osteocalcin in the sixth decade in women, indicate that aging is associated with a decrease in bone formation and turnover and that osteoblastic activity and bone turnover are stimulated at the menopause.

Seasonal variation in bone metabolism in young healthy subjects

SummarySerum vitamin D metabolites and urinary calcium excretion; parameters of bone formation (serum alkaline phosphatase, serum osteocalcin); parameters of bone resorption (24 hour hydroxyprolinuria, 2 hour fasting urinary hydroxyproline/creatinine ratio); and parameters of cortical and trabecular bone density, parathyroid hormone (iPTH, COOH terminal assay), and serum minerals (calcium, phosphorus) were followed serially in 55 young adults (21 women and 34 men) from December 1985 until January 1987 at four different times during the year. The effect of a low-dose cyclooxygenase inhibitor (piroxicam 5 mg daily) on the same parameters of bone density and bone turnover when given from December until May, was also evaluated in this study. At the end of the treatment period parameters of bone turnover and bone density were comparable between placebo and piroxicam-treated groups. Therefore, the results of all subjects were pooled in order to investigate seasonal variation. In both sexes, seasonal variation was found not only for 250HD3 but also for 1,25(OH)2D3, serum calcium and phosphorus, urinary calcium excretion, and for bone density at the lumbar spine. Parameters of bone formation (serum osteocalcin and alkaline phosphatase), bone resorption (24 hour urinary hydroxyprolinuria and fasting urinary hydroxyproline/creatinine ratio) and PTH were influenced by this seasonal variation. We conclude that in young adults, a significant seasonal variation occurs, with low winter and high summer values, for serum 25 and 1,25(OH)2D3 for urinary calcium apparently without important influence on parameters of bone turnover or parathyroid activity and for lumbar spine density. Treatment with a low-dose cyclooxygenase inhibitor was without influence on the observed changes.

Collagen and non-collagenous protein content (osteocalcin, sialoprotein, proteoglycan) in the iliac crest bone and serum osteocalcin in women with and without hand osteoarthritis

Quantitative and qualitative variations in bone composition were studied in postmortem iliac crest bone specimens from 32 women aged 60 to 75, grouped according to the presence of osteoarthritis at the hand joints. The EDTA extraction yield of macromolecules was significantly greater in the osteoarthritis group. Collagen and osteocalcin content were significantly increased and proteoglycan content decreased in the osteoarthritis group. No difference in sialoprotein content was found. In a clinical study of 20 patients with generalised osteoarthritis, we found compared to 15 controls also significantly increased serum levels of osteocalcin. These results indicate in an unselected group of cases that differences in bone matrix constituents exist between elderly women with and without an osteoarthritic constitution. The finding that these alterations are present even far away from the articular lesion, and the fact that the serum osteocalcin levels are elevated, indicate that osteoarthritis is part of a more generalised bone disease and not a purely cartilage disease.

Collagen and Non-Collagenous Proteins in Different Mineralization Stages of Human Femur

Mineralized tissues exhibit varying degrees of mineralization in different areas within the same bone. Using the technique of density gradient fractionation, bone powder from the diaphysis of human femur has been separated in different fractions corresponding to the degree of mineralization. Isolated bone fractions were analysed for their content in collagen and non-collagenous proteins. The results showed marked differences between compact and spongy bones, this latter containing higher proportions of little mineralized bone particles than the former (p less than 0.01). The ethylenediaminetetra-acetic acid (EDTA) extractability and the bone matrix size decreased relative to the decrease in specific gravity of bone particles. Among the matrix components of different fractions, sialoprotein consistently increased with the increase in specific gravity while proteoglycan decreased in reverse manner to the increase in collagen. However, in the most mineralized fraction (specific gravity: 2.33 g/cm3), the proteoglycan amount increased while collagen decreased. In conclusion, this study of bone maturation in human femur confirms the suitability of the technique of density gradient fractionation in the studies of bone matrix-mineral interactions. Apart from the fraction with the highest specific gravity, the analytical results obtained in fractions are similar to those observed in age-related bone changes, suggesting that the increase in mineralization degree of bone particles may be related to their age.

Studies on EDTA extracts and collagenase digests from osteoporotic cancellous bone of the femoral head.

Using EDTA extraction and collagenase digestion, cancellous bone of the femoral heads from 10 normal and 9 osteoporotic subjects were analyzed for their contents of collagen, sialoprotein, proteoglycan and carbohydrate. The percentage of extracted matrix proteins of the osteoporotic bone in EDTA was significantly decreased, as was the collagenase-resistant fraction (p less than 0.05). The sialic acid level in osteoporotic bone matrix was lower than in controls (p less than 0.05). The alterations found in bone matrix constituents in osteoporotic bone relative to controls suggest that in osteoporosis and fractures, not only bone mass changes, but also bone quality changes play a role in bone strength.