Rat Serum Osteocalcin Concentration Is Determined by Food Intake and Not by Inflammation

Abstract

Osteocalcin, or bone gla protein, is the major noncollagenous protein in bone. Previous findings of decreased serum osteocalcin concentrations in children with Kwashiorkor led us to analyze the respective influence of nutritional status and inflammation on circulating osteocalcin in growing rats. Food deprivation for 72 h induced a significant 24% decrease in serum osteocalcin. Refeeding produced a rapid rise in serum osteocalcin, which reached control concentrations after 24 h of refeeding. Bone osteocalcin was not affected by these dietary manipulations. The changes in serum osteocalcin were not correlated with serum 1,25-dihydroxycholecalciferol, whereas they could be related to serum 25-hydroxycholecalciferol concentrations. Turpentine injection reduced serum osteocalcin concentration, but pair-feeding showed that this decrease was entirely attributable to spontaneous food restriction and not to inflammation. By contrast, the sensitive nutritional marker, serum transthyretin, was affected by both inflammation and food restriction. These results indicate that serum osteocalcin is closely related to food intake but not to inflammation, suggesting that the dramatic decrease in serum osteocalcin that we previously observed in children with Kwashiorkor is due to malnutrition per se.

Serum Osteocalcin Regulation in Protein-Energy Malnourished Children

“…However, a comparison between eight infected and nine noninfected children of the CD group did not show any difference in serum osteocalcin (1.94 ± 0.42 versus 2.06 ± 0.26 nmol/L, respectively). These results are in accordance with our previous finding showing that, in rats, serum osteocalcin is not affected by experimental inflammation (21). Therefore, these studies suggest that the low serum osteocalcin concentrations found in malnourished children were independent of inflammatory status.…”

“…Indeed, we have found in 3-day starved rats a significant decrease in serum osteocalcin without any change in the concentration of serum 1,25(OH)2D (21). Serum iPTH, another potential regulator of osteocalcin production (27), cannot explain a low serum osteocalcin level in PEM, because iPTH concentrations were similar in marasmic and CD control groups.…”

Impacts of restricted feeding and realimentation on bone development and plasma concentrations of bone-specific biomarkers in lambs

“…This result, however, suggested that the osteoblast cell numbers in feed-restricted groups were probably compensated to attain AD group during the early stage in realimentation and resulted in similar activity when compared with ad libitum fed lambs. Similar results were reported by Ndiaye et al (1992) who found that refeeding produced a rapid rise in rat serum osteocalcin, which reached control concentrations after 24 h of refeeding.…”

“…Reduced plasma concentration of osteocalcin in the feed-restricted lambs might result from decreased activity by osteoblasts (Clemens and Karsenty, 2011). Ndiaye et al (1992) and Scott et al (1997) showed that osteocalcin concentration was reduced by energy restriction and these changes resulted mainly from reduction of bone formation. While osteocalcin is the major non-collagenous protein in bone, its function is unknown, although its close association with the mineral matrix had been taken to indicate some role in the mineralization process.…”

“…Those used to monitor the bone formation are products of the osteoblast, including osteocalcin and bone-specific alkaline phosphatase (ALP), and were reported to reflect the activity of these cells in bone (Nicodemo et al, 1999). Feed intake was an important determinant of blood osteocalcin concentration and bone formation (Ndiaye et al, 1992;Scott et al, 1997). Prentice et al (2006) reported that serum concentration of osteocalcin was low in children suffering from protein-energy malnutrition and increased significantly during nutritional recovery.…”