Crepaldi G, Romanato G, Tonin P, Maggi S
CNR Institute of Neuroscience, Aging Section, University of Padua, 35128 Padua, Italy.
J Endocrinol Invest. 2007;30(6 Suppl):42-7.
The Epidemiologic Study on the Prevalence of Osteoporosis in Italy showed that the prevalence of osteoporosis among women and men aged 60 yr and over is 22.8% and 14.5%, respectively, giving rise to about 80,000 new fractures a yr. Sarcopenia is considered to be one of the main features of the aging process. It is characterized by a reduction in muscle mass and muscle strength, and affects women more than men. It is associated with a increased risk of fractures consequent upon a greater predisposition to falls, but also to the lack of bone remodeling due to reduced muscle mechanical strength. Muscle strength determines quality bone modifications such as density, strength, and microarchitecture. Variations in the ratios of cortical and muscle areas give rise to various types of osteoporosis, with different risks of fracture. Bone mineral density increases with body fat mass, and obesity has a protective effect against osteoporosis. This protective effect is explained by a combination of hormonal (peripheral aromatization of androgens to estrogens in adipose tissue) and mechanical factors (on weight-bearing bone sites), but the hormone leptin also probably mediates fat and bone mass. Serum leptin levels are closely related to body fat mass, and some findings suggest the peripheral effect of leptin, which exerts estrogenic effects, enhancing osteoblastic differentiation and inhibiting late adipocytic differentiation. The overall effect of leptin on bone results from a balance between negative central effects and positive direct peripheral effects, according to serum leptin levels.
意大利骨质疏松症患病率的流行病学研究表明，60岁及以上女性和男性的骨质疏松症患病率分别为22.8%和14.5%，每年导致约8万例新骨折。肌肉减少症被认为是衰老过程的主要特征之一。其特点是肌肉质量和肌肉力量下降，对女性的影响大于男性。它与因更容易跌倒以及由于肌肉机械强度降低导致的骨重塑缺乏而增加的骨折风险相关。肌肉力量决定了诸如密度、强度和微结构等优质骨的改变。皮质面积与肌肉面积的比例变化会导致各种类型的骨质疏松症，骨折风险各不相同。骨矿物质密度随体脂量增加，肥胖对骨质疏松症有保护作用。这种保护作用可以通过激素（脂肪组织中雄激素外周芳香化为雌激素）和机械因素（在负重骨部位）的共同作用来解释，但瘦素激素可能也介导了脂肪和骨量。血清瘦素水平与体脂量密切相关，一些研究结果表明瘦素的外周作用，它发挥雌激素作用，增强成骨细胞分化并抑制晚期脂肪细胞分化。根据血清瘦素水平，瘦素对骨骼的总体作用源于中枢负性作用和外周正性直接作用之间的平衡。
