Dimarco Nancy M, Dart Lyn, Sanborn Charlotte Barney
Department of Nutrition and Food Sciences, Texas Woman's Univ., Denton, TX 76204-5888, USA.
J Appl Physiol (1985). 2007 Nov;103(5):1469-78. doi: 10.1152/japplphysiol.01137.2005. Epub 2007 Aug 9.
The exercising woman with nutritional deficits and related menstrual irregularities is at risk of compromising long-term bone health, i.e., the female athlete triad. There is no animal model of the female athlete triad. The purpose of this study was to examine long-term energy restriction in voluntary wheel-running female rats on estrous cycling, bone mineral content, and leptin levels. Twelve female Sprague-Dawley rats (age 34 days) were fed ad libitum and given access to running wheels during an initial 14-wk period, providing baseline and age-related data. Daily collection included dietary intake, body weight, estrous cycling, and voluntary running distance. At 4 mo, rats were randomized into two groups, six restrict-fed rats (70% of ad libitum intake) and six rats continuing as ad libitum-fed controls. Energy intake, energy expenditure, and energy availability (energy intake - energy expenditure) were calculated for each animal. Serum estradiol and leptin concentrations were measured by RIA. Femoral and tibial bone mineral density and bone mineral content (BMC) were determined by dual-energy X-ray absorptiometry. Restrict-fed rats exhibited a decrease in energy availability during Weight Loss and Anestrous phases (P = 0.002). Compared with controls after 12 wk, restrict-fed rats showed reduced concentrations of serum estradiol (P = 0.002) and leptin (P = 0.002), lower ovarian weight (P = 0.002), and decreased femoral (P = 0.041) and tibial (P = 0.05) BMC. Decreased energy availability resulted in anestrus and significant decreases in BMC, estrogen and leptin levels, and body weight. Finally, there is a critical level of energy availability to maintain estrous cycling.
患有营养缺乏和相关月经不调的运动女性有损害长期骨骼健康的风险，即女性运动员三联征。目前尚无女性运动员三联征的动物模型。本研究的目的是研究自愿进行轮转运动的雌性大鼠长期能量限制对发情周期、骨矿物质含量和瘦素水平的影响。12只雌性Sprague-Dawley大鼠（34日龄）在最初的14周内自由进食并可使用转轮，以提供基线和与年龄相关的数据。每天收集的指标包括饮食摄入量、体重、发情周期和自愿跑步距离。4个月时，将大鼠随机分为两组，六只限制喂养大鼠（自由摄入量的70%）和六只继续自由喂养的对照大鼠。计算每只动物的能量摄入、能量消耗和能量可利用性（能量摄入 - 能量消耗）。通过放射免疫分析法测定血清雌二醇和瘦素浓度。通过双能X线吸收法测定股骨和胫骨的骨矿物质密度和骨矿物质含量（BMC）。限制喂养的大鼠在体重减轻和发情间期能量可利用性降低（P = 0.002）。与12周后的对照组相比，限制喂养的大鼠血清雌二醇（P = 0.002）和瘦素（P = 0.002）浓度降低，卵巢重量减轻（P = 0.002），股骨（P = 0.041）和胫骨（P = 0.05）BMC降低。能量可利用性降低导致发情间期以及BMC、雌激素和瘦素水平及体重显著下降。最后，存在一个维持发情周期的关键能量可利用水平。
