NUTRITIONAL REGULATION OF BONE TURNOVER

骨质疏松症影响着大约2800万美国人，是一个 老年男女的死因。据估计，在 女性(50岁以上)，高达50%患有骨量减少(低骨量)，18%有 骨质疏松。低体重或低体重女性患骨质疏松的风险增加 那些有减肥史的人。此外，私家侦察显示， 在肥胖女性中，适度的体重减轻会导致骨骼松动和丢失。 此外，对非自愿重量损失的研究表明，骨骼的大小 苗条的女性比体重较重的女性损失更大。因此，这些研究将 解决超重(身体质量)时骨移动和丢失是否更严重的问题 绝经前和绝经后肥胖(BMI大于30)相比，BMI在25-29.9之间 女性在适度自愿减重期间。我们的数据显示， 血清甲状旁腺激素(PTH)和性激素的下降可能是 调节有体重损失的骨转换的上升。据推测，一个 卡路里限制期间钙吸收减少是导致 甲状旁腺素升高。我们建议研究营业额和PTH上升的基础 在卡路里限制期间通过检查总的钙吸收分数 在重量损失期间。在肥胖女性中，PIS发现每天1.6毫克的钙可以抑制 与体重丢失相关的骨松动和丢失。然而，它并不是 是否知道这一水平的钙摄入量会抑制“瘦身”患者的骨动员 卡路里限制期间超重的女性。此外，也有可能是 目前推荐的摄入量水平(1-1.2克/天)在体重减少期间是不够的 基于前人对体重丢失引起的骨丢失的研究。因此，这些 研究将检查2卡路里限制期间的骨转换和骨质量 钙的摄入水平(适量或高)，以确定体重损失的最佳水平。 重要的是，老鼠研究表明，骨折的风险随着热量的增加而增加 限制(尽管摄入足够的钙)。为了了解骨骼的质量如何 随着wt损失而改变，并且它是否取决于初始主体wt，我们 将检查慢性热量摄入后骨骼的超微结构特性 限制肥胖和瘦小的大鼠。这些研究的长期目标是 确定营养对骨骼的影响，可用于预防 以及骨质疏松症的治疗。

Osteoporosis affects approximately 28 million Americans, and is a leading cause of death among older men and women. It has been estimated that in women (50+ years), up to 50% have osteopenia (low bone mass) and 18% have osteoporosis. The risk of osteoporosis increases in women of low body weight or those who have a history of weight loss. In addition, the PIs have shown that moderate weight loss results in bone mobilization and loss in obese women. Moreover, studies of involuntary wt loss show that the magnitude of the bone loss is greater in thinner than heavier women. Hence, these studies will address whether bone mobilization and loss is greater in overweight (body mass index, BMI 25-29.9) than obese (BMI more than 30 ) pre- and post menopausal women during moderate voluntary wt loss. Our data show that an increase in serum parathyroid hormone (PTH) and a decrease in sex hormones may be regulating the rise in bone turnover with wt loss. It is hypothesized that a reduced calcium absorption during caloric restriction is responsible for the rise in PTH. We propose to study the basis for the rise in turnover and PTH during caloric restriction by examining total fractional calcium absorption during wt loss. In obese women, the PIs found that 1.6 mg/d of Ca can suppress the bone mobilization and loss associated with wt loss. However, it is not known if this level of Ca intake can suppress bone mobilization in "thinner" overweight women during caloric restriction. Also, it is possible that the current recommended level of intake (1-1.2 g/d) is not adequate during wt loss based on studies of wt loss induced bone loss by others. Therefore, these studies will examine bone turnover and mass during caloric restriction at 2 levels of Ca intake (adequate or high) to determine optimal levels for wt loss. Importantly, rat studies show that fracture risk is increased with caloric restriction (despite adequate Ca intake). To understand how the quality of bone is altered with wt loss, and whether it is dependent on initial body wt, we will examine the ultrastructural properties of bone after chronic caloric restriction in obese and lean rats. Long-term goals of these studies are to determine nutritional influences on bone which can be applied in the prevention and treatment of osteoporosis.