Ndiaye B, Cournot G, Pélissier M A, Debray O W, Lemonnier D
INSERM-GERM, Faculté de Médecine Xavier Bichat, Paris, France.
J Nutr. 1995 May;125(5):1283-90. doi: 10.1093/jn/125.5.1283.
We studied the effects of energy restriction on serum osteocalcin concentration and bone formation rate in rats. The experiment was designed to achieve energy restriction by reducing the carbohydrate intake while providing identical quantities of protein, fat, vitamins and minerals. Energy intakes of three groups of post-weaning male rats were restricted by 20, 40 and 60% for 4 wk. Serum calcium, phosphorus, transthyretin, triiodothyronine (T3), thyroxine (T4), 1,25-dihydroxycholecalciferol, 25-hydroxycholecalciferol and immunoreactive parathyroid hormone (iPTH) concentrations were determined. Energy restriction (20, 40 and 60%) produced a significant and gradual drop of serum osteocalcin concentrations, although the serum concentrations of its key regulators, i.e., 1,25-dihydroxycholecalciferol and iPTH, were not significantly affected. On the contrary, serum concentrations of calcium, phosphorus, transthyretin, T3 and T4 were significantly lower in the energy-restricted groups. However, our results do not support their implication in the regulation of serum osteocalcin synthesis by energy intake. Serum osteocalcin concentration was positively correlated with bone mineral apposition (r = 0.50, P < 0.05) and bone mineralization (r = 0.50, P < 0.05) rates suggesting that its decrease resulted from a reduction of bone formation, and not from abnormal mineralization, because osteoid seam thickness was not modified. Energy intake seems to be an important determinant of serum osteocalcin concentration and bone formation; however, the exact mechanism underlying this regulation remains to be determined.
我们研究了能量限制对大鼠血清骨钙素浓度和骨形成率的影响。实验设计通过减少碳水化合物摄入量，同时提供等量的蛋白质、脂肪、维生素和矿物质来实现能量限制。三组断奶后雄性大鼠的能量摄入在4周内分别限制了20%、40%和60%。测定了血清钙、磷、转甲状腺素蛋白、三碘甲状腺原氨酸（T3）、甲状腺素（T4）、1,25-二羟胆钙化醇、25-羟胆钙化醇和免疫反应性甲状旁腺激素（iPTH）的浓度。能量限制（20%、40%和60%）导致血清骨钙素浓度显著且逐渐下降，尽管其关键调节因子即1,25-二羟胆钙化醇和iPTH的血清浓度未受到显著影响。相反，能量限制组的血清钙、磷、转甲状腺素蛋白、T3和T4浓度显著较低。然而，我们的结果并不支持它们参与能量摄入对血清骨钙素合成的调节。血清骨钙素浓度与骨矿物质沉积率（r = 0.50，P < 0.05）和骨矿化率（r = 0.50，P < 0.05）呈正相关，这表明其下降是由于骨形成减少，而非矿化异常，因为类骨质缝厚度未改变。能量摄入似乎是血清骨钙素浓度和骨形成的一个重要决定因素；然而，这种调节的具体机制仍有待确定。
